WO2013074057A1

WO2013074057A1 - Method and apparatus for thermoelectric cooling of fluids

Info

Publication number: WO2013074057A1
Application number: PCT/US2011/001914
Authority: WO
Inventors: Uttam Ghoshal; Ayan Guha; Himanshu Pokharna
Original assignee: Sheetak, Inc.
Priority date: 2011-11-17
Filing date: 2011-11-17
Publication date: 2013-05-23
Also published as: EP2807432A1; US20140318152A1

Abstract

The present disclosure provides a method and a thermoelectric cooling apparatus for cooling a fluid. The thermoelectric cooling apparatus comprises one or more of thermoelectric devices, a hot sink, a cold sink, and a heat rejection apparatus which comprises condenser fins and a fan to attain a high figure of merit. The heat from the fluid is transferred to the hot sink and/or one or more heat pipes by the one or more thermoelectric devices. The heat from the one or more heat pipes is dissipated to the ambient through condenser fins and the fan.

Description

METHOD AND APPARATUS FOR THERMOELECTRIC COOLING OF FLUIDS BACKGROUND

The present disclosure relates to thermoelectric cooling of fluids. More specifically, it relates to an efficient method and a device for thermoelectric cooling of fluids.

The most widely used type of cooling system is a vapor compression system, which uses chlorofluorocarbon (CFC)-based refrigerants to cool fluids. It has a high coefficient of performance (COP). However, the use of CFC-based refrigerants in the vapor compression system for cooling poses an environmental threat because CFCs may lead to a depletion of the ozone layer.

An alternative to the vapor compression system for cooling fluids is a

thermoelectric cooling system which is environment friendly, effective, and simple in construction. However, there exists a limitation in the thermoelectric cooling system - its COP is about one third the COP of a vapor compression system. To increase the COP of the thermoelectric cooling system, much effort has been made in the past to optimize its heat dissipation methods and device level designs, among other things.

Other limitations of conventional thermoelectric cooling systems include poor power utilization techniques. Continuously switching ON the thermoelectric cooling system results in increased power consumption, thereby increasing the cost of cooling per liter of fluid.

While thermoelectric cooling systems and methods for their operation have been developed in the past, there exists a need for further development in designing thermoelectric cooling systems to increase the COP.

SUMMARY An objective of the present disclosure is to provide a thermoelectric cooling apparatus with an improved design and a high co-efficient of performance. Though the thermoelectric cooling apparatus according to the present disclosure is used to cool fluids, other forms of materials such as semi-liquids, semi-solids, colloids, and gels phased substances, can also be cooled using the thermoelectric cooling apparatus disclosed.

In an embodiment of the present disclosure, a thermoelectric cooling apparatus comprises one or more thermoelectric devices, one or more metal standoffs, a cold sink, one or more heat pipes and condenser fins. The one or more thermoelectric devices are configured to cool a fluid, the one or more thermoelectric devices comprising a hot side and a cold side. The one or more metal standoffs comprise a first side and a second side. The first side of the one or more metal standoffs is attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices. The cold sink is attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs. The one or more heat pipes comprise a first end and a second end. The first end is attached to the hot side of the one or more thermoelectric devices, wherein the one or more heat pipes are configured to assist in transfer of heat from the hot side of the one or more thermoelectric devices to the ambient. The condenser fins are attached to the second end of the one or more heat pipes. The condenser fins are configured to assist in dissipating heat from the second end of the one or more heat pipes to the ambient.

The thermoelectric cooling apparatus according the present embodiment further comprises a hot sink attached to the first end of the one or more heat pipes, wherein the hot sink is configured to assist in dissipating heat from the first end of the one or more heat pipes.

The thermoelectric cooling apparatus according the present embodiment may further comprise a plurality of screws, wherein the plurality of screws is configured to facilitate attachment of the hot sink and the cold sink.

The thermoelectric cooling apparatus according the present embodiment may further comprise a plurality of grommets, wherein the plurality of grommets is configured to prevent heat conduction from the hot sink to the cold sink. The thermoelectric cooling apparatus according the present embodiment may further comprise a hot sink fan thermally coupled to the hot sink, wherein the fan is configured to dissipate heat from the hot sink to the ambient.

The thermoelectric cooling apparatus according the present embodiment may further comprise a fan thermally coupled to the condenser fins, wherein the fan is configured to dissipate heat from the condenser fins to the ambient.

The thermoelectric cooling apparatus according the present embodiment may further comprise an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices.

In the thermoelectric cooling apparatus of above explained embodiment, the cold sink comprises at least one of anodized aluminum, copper and nickel.

The thermoelectric cooling apparatus according to the present embodiment may further comprise an insulation material, wherein the insulation material is configured to fill gaps between elements of the thermoelectric cooling apparatus.

The thermoelectric cooling apparatus according to the present embodiment may further comprise a thermal diode positioned between the hot side of the one or more thermoelectric devices and the one or more heat pipes, wherein the thermal diode is configured for unidirectional heat transfer. The thermoelectric cooling apparatus according to the present embodiment may further comprise one or more containers containing the fluid, wherein one of the one or more containers is configured to function as a thermal capacitor.

A thermoelectric cooling apparatus in accordance with another embodiment comprises one or more thermoelectric devices, a cold sink, one or more diodic heat pipes, and a fin array. The one or more thermoelectric devices comprise a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid. The cold sink is attached to the cold side of the one or more thermoelectric devices, the cold sink being configured to transfer heat from the fluid to the one or more thermoelectric devices. The one or more diodic heat pipes comprise a first end and a second end The first end of one or more diodic heat pipes is attached to the hot side of the one or more thermoelectric devices, wherein the one or more diodic heat pipes are configured to facilitate transfer heat from the hot side of the one or more thermoelectric devices to the ambient. The fin array is attached to the second end of the one or more heat pipes, wherein the fin array is configured to transfer heat from the second end of the one or more heat pipes.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise condenser fins attached to the one or more heat pipes, wherein the condenser fins are configured to assist in dissipation of heat from the one or more heat pipes.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise a fan thermally coupled to the condenser fins, wherein the fan is configured to dissipate heat from the condenser fins to the ambient.

A thermoelectric cooling apparatus in accordance with yet another embodiment comprises one or more thermoelectric devices, one or more metal standoffs, one or more cold sinks, and one or more heat pipes. The one or more thermoelectric devices comprise a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid. The one or more metal standoffs comprise a first side and a second side. The first side of the one or more metal standoffs is attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices. The one or more cold sinks are attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs. The one or more heat pipes comprise a first end and a second end. The first end of the one or more heat pipes is attached to the hot side of the one or more thermoelectric devices, wherein the one or more heat pipes are configured to assist in dissipating heat from the hot side of the one or more thermoelectric devices to the ambient

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise condenser fins and a fan, the condenser fins being attached to the second end of the one or more heat pipes, wherein the condenser fins and the fan are configured to dissipate heat from the one or more heat pipes to the ambient.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise an insulated section to prevent the conduction of heat from the second end to the first end of the one or more heat pipes.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices. A thermoelectric cooling apparatus in accordance with yet another embodiment comprises one or more thermoelectric devices, one or more metal standoffs, a cold sink, and a separator. The one or more thermoelectric devices comprise a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid. The one or more metal standoffs comprise a first side and a second side. The first side of the one or more metal standoffs is attached to the cold side of the one or more

thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices. The cold sink is attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs. The separator is configured to direct the fluid towards the cold sink. The separator may comprise a plurality of pores.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise a convective heat dissipation apparatus thermally coupled to the hot side of the one or more thermoelectric devices. The convective heat dissipation apparatus is configured to remove heat from the hot side of the one or more

thermoelectric devices to the ambient, wherein the convective heat dissipation

apparatus comprises a convective fluid for heat transportation, a heat spreader, a pump, fins and a fan.

A thermoelectric cooling apparatus with yet another embodiment comprises one or more thermoelectric devices, one or more metal standoffs, a cold sink and a heat pipe-heat sink assembly. The one or more thermoelectric devices comprise a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid. The one or more metal standoffs comprise a first side and a second side. The first side of the one or more metal standoffs is attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices. The cold sink is attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs. The heat pipe-heat sink assembly is attached to the hot side of the one or more thermoelectric devices, wherein the heat pipe-heat sink assembly is configured to dissipate heat from the hot side of the one or more thermoelectric devices to the ambient.

The thermoelectric cooling apparatus in accordance with the present embodiment may further comprise a fan thermally coupled to the heat pipe-heat sink assembly, wherein the fan is configured to dissipate heat from the heat pipe-heat sink assembly to the ambient.

A method of cooling a fluid by using a thermoelectric apparatus comprises operating the thermoelectric apparatus at optimum conditions when the temperature of the fluid is not within a predetermined temperature range, determining the temperature of the fluid at predetermined time intervals, and operating the thermoelectric apparatus at steady state conditions when the temperature of the fluid is within the predetermined temperature range.

Further, in the method according to the present embodiment, operating the thermoelectric apparatus at optimum conditions includes supplying an optimum current (l₀pt) to the thermoelectric apparatus. Furthermore, in the method according to the present embodiment, operating the thermoelectric apparatus at steady state conditions includes supplying a steady state current (Iss) to the thermoelectric apparatus.

In an embodiment of the present disclosure, a method of operating a

thermoelectric cooling apparatus for cooling a fluid is disclosed. According to the embodiment, the method comprises selecting at least one mode of operation from a plurality of modes of operation for the thermoelectric cooling apparatus, and supplying maximum voltage (V_max) or minimum voltage (V_min) to the thermoelectric cooling apparatus based on the selected mode of operation.

The plurality of modes according to the present method, includes a high power mode and a power efficiency mode.

Further, the method in accordance with the present embodiment further comprises switching from V_min to V_max when the temperature of the fluid is greater than predetermined temperature (T_w).

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the disclosure will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the disclosure, wherein like designations denote like elements, and in which

FIG. 1 illustrates a side view of a thermoelectric cooling unit, in accordance with an embodiment of the present disclosure;

FIG. 2 illustrates a perspective view of a thermoelectric cooling unit, in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates a perspective view of a thermoelectric cooling apparatus, in accordance with an embodiment of the present disclosure; FIG. 4 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with an embodiment of the present disclosure;

FIG. 5 illustrates a cross-sectional view of a thermoelectric cooling unit, in accordance with another embodiment of the present disclosure;

FIG. 6 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with another embodiment of the present disclosure; FIG. 7 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 8 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure; FIG. 9 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 10 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 11 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 12 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 13 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure; FIG. 14 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 15 illustrates a cross-sectional view of a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure;

FIG. 16 illustrates graphs depicting variations in temperature and current with time for a thermoelectric cooling apparatus, in accordance with an embodiment of the present disclosure;

FIG. 17 illustrates graphs depicting variations in temperature and current with time for a thermoelectric cooling apparatus, in accordance with another embodiment of the present disclosure; FIG. 18 illustrates graphs depicting variations in temperature and current with time for a thermoelectric cooling apparatus, in accordance with yet another embodiment of the present disclosure; and

FIG. 19 illustrates a flow chart representing a method of operation of a

thermoelectric cooling apparatus.

DESCRIPTION OF EMBODIMENTS

Before describing the embodiments in detail, in accordance with the present disclosure, it should be observed that these embodiments reside primarily in the method and apparatus for cooling of fluids. Accordingly, steps of the method and the apparatus components have been represented to show only those specific details that are pertinent for an understanding of the embodiments of the present disclosure, and not the details that will be apparent to those with ordinary skill in the art.

FIG.1 illustrates a side view of a thermoelectric cooling unit 100, in accordance with an embodiment of the present disclosure. The thermoelectric cooling unit 100 comprises thermoelectric devices 102, metal standoffs 104, a cold sink 106, a hot sink 108, heat pipes 110, condenser fins 114, and a fan 116.

The thermoelectric devices 102 comprise a hot side and a cold side (not shown in the figure). In an embodiment of the present disclosure, thermoelectric devices 102 comprises thermoelectric modules of different Q_max (Q_max is defined as the maximum cooling capacity of the thermoelectric module for ΔΤ = 0). The cold side of thermoelectric devices 102 is thermally connected to cold sink 106 through metal standoffs 104. Metal standoffs 104 are configured to transfer heat from cold sink 106 to thermoelectric devices 102. Metal standoffs 104 further prevent thermal losses by increasing the separation between the hot side of thermoelectric devices 102 and cold sink 106. Cold sink 106 is in contact with a fluid (not shown in the figure). The hot side of thermoelectric devices 102 is attached to hot sink 108. In an embodiment of the present disclosure, hot sink 108 is made of extruded anodized aluminum. In another embodiment of the present disclosure, hot sink 108 comprises metals such as nickel, which prevent surface oxidation and facilitates soldering. Hot sink 108 and cold sink 106 comprise a plurality of fins that are optimized for natural convection in the fluid. Hot sink 108 and cold sink 106 are physically connected using screws 118. Grommets 112 prevent conduction from hot sink 108 to cold sink 106 through screws 118. Further, heat pipes 110 are positioned between the hot side of thermoelectric devices 102 and hot sink 108. Heat pipes 110 comprise a first end and a second end (not shown in figure). The first end of heat pipes 110 is attached to the hot side of thermoelectric devices 102. In an embodiment of the present disclosure, each of thermoelectric devices 102 is connected to each of heat pipes 110. The second end of heat pipes 110 is connected to condenser fins 114. In an embodiment of the present disclosure, heat pipes 110 are unidirectional, i.e. they conduct heat in only one direction, from the first end to the second end. In another embodiment of the present disclosure, heat pipes 110 are bidirectional, i.e. they conduct heat in both directions based on the temperature gradient. When thermoelectric devices 102 are switched ON, heat is extracted from the fluid through cold sink 106 and metal standoffs 104, thus cooling the fluid.

Thermoelectric devices 102 transfer heat from cold sink 106 and metal standoffs 104 to the hot side of thermoelectric devices 102. The heat is dissipated from the hot side through a heat transfer assembly and hot sink 108. The heat transfer assembly comprises heat pipes 110, condenser fins 1 14 and fan 116. In an embodiment of the present disclosure, hot sink 108 is in contact with the fluid to be cooled. A part of the heat is transferred to the fluid to be cooled so that the fluid to be cooled acts as a thermal capacitor.

FIG.2 illustrates a perspective view of a thermoelectric cooling unit 200, in accordance with an embodiment of the present disclosure.

Apart from the elements mentioned in conjunction with FIG. 1 , thermoelectric cooling unit 200 comprises a shell 202, an insulation material 204 and grooves 210.

Shell 202 encloses thermoelectric devices 102 (described in conjunction with FIG. 1), the first end of heat pipes 110, and metal standoffs 104 (described in conjunction with FIG. 1) with the aid of insulation material 204. Insulation material 204 is configured to fill gaps between elements of thermoelectric cooling unit. In an embodiment of the present disclosure, insulation material 204 is spray type foam. Insulation material 204 fills gaps between elements of thermoelectric cooling unit 200 such as thermoelectric devices 102 and metal standoffs 104, in accordance with the present embodiment. The thermoelectric cooling unit 200 further comprises a first hole 206 and a second hole 208 formed in the insulation. First hole 206 allows a warm fluid (described in conjunction with FIG. 3) to flow from a top container to a bottom container (described in conjunction with FIG. 3). Second hole 208 is configured to prevent an air lock that can be caused due to the transfer of the warm fluid from the top container to the bottom container.

Further, grooves 210 are present at a top side and a bottom side of

thermoelectric cooling unit 200. In the insulation, grooves 210 are configured to position O-rings and to fit the top container and the bottom container. In an embodiment of the present disclosure, O-rings are rubber gaskets. Usage of the rubber gaskets makes the assembly fluid tight. Fins 212 of hot sink 108 are in thermal contact with the warm fluid present in the input container. Similarly, fins 214 of cold sink 106 are in thermal contact with the cold fluid present in the output chamber. In an embodiment of the present disclosure, fins 212 and 214 are made of aluminum.

The warm fluid present at the input container flows to the output container through first hole 206. Cold sink 106 is in thermal contact with the cold fluid. When thermoelectric devices 102 are switched ON, heat from the cold fluid is transferred to the hot side of thermoelectric devices 102 through cold sink 106. A first portion of the heat dissipated at the hot side of thermoelectric devices 102 is transferred to hot sink 108 and the warm fluid. A second portion of the heat dissipated at the hot side of thermoelectric devices 102 is transferred to the ambient through heat pipes 110 and condenser fins 114.

FIG. 3 illustrates a perspective view of a thermoelectric cooling apparatus 300, in accordance with an embodiment of the present disclosure. Thermoelectric cooling apparatus 300 comprises a thermoelectric cooling unit 200, a top container 302, a bottom container 304, a fluid storage chamber 306, a fluid dispenser 312, and an insulated pipe 314.

Fluid storage chamber 306 stores a warm fluid 308 that needs to be cooled.

Warm fluid 308 is also present in top container 302. Warm fluid 308 present in top container 302 is in thermal contact with hot sink 108 of thermoelectric cooling unit 200. In an embodiment of the present disclosure, top container 302 that comprises the warm fluid 308 acts as a thermal capacitor. The outer body of top container 302 is made of materials such as plastic or thin metal sheet, which may aid in discharging the thermal capacitor. Warm fluid 308 is transferred from fluid storage chamber 306 to bottom container 304 through insulated pipe 314 that connects fluid storage chamber 306 and bottom container 304. Bottom container 304 comprises cold fluid 310. In an embodiment of the present disclosure, bottom container 304 is insulated to prevent heat leakage from the ambient to cold fluid 310. The walls of the bottom container 304 are made of either plastic material or thin metal sheet. Cold fluid 310 is dispensed out of bottom container 304 through fluid dispenser 312.

When thermoelectric cooling unit 200 is switched ON, heat from cold fluid 310 is transferred to warm fluid 308 present in top container 302. Cold fluid 310 is dispensed from the bottom container 304 through fluid dispenser 312. As the level of cold fluid 310 decreases in bottom container 304, warm fluid 308 is dispensed from fluid storage chamber 306 to bottom container 304 through insulated pipe 314. Insulated pipe 314 prevents transfer of heat from warm fluid 308 present in top container 302 to warm fluid 308 which is transferred from fluid storage chamber 306 to bottom container 304.

FIG.4 illustrates a cross-sectional view of a thermoelectric cooling apparatus 400, in accordance with another embodiment of the present disclosure.

Apart from the elements mentioned in conjunction with FIG. 1 , FIG. 2, and FIG. 3, thermoelectric cooling apparatus 400 comprises a separator 402. Separator plate 402 is present in bottom container 304 and positioned below first hole 206. In an embodiment of the present disclosure, separator 402 is made of plastic. Separator 402 directs the flow of warm fluid 308 toward cold sink 108 and ensures that warm fluid 308 from top container 302 does not directly reach the bottom portion of bottom container 304 and that warm fluid 308 contacts cold sink 106. Warm fluid 308 is cooled when it comes in contact with cold sink 106. Cold fluid 310 is heavier and denser than warm fluid 308, and thus reaches the bottom portion of bottom container 304. Cold fluid 310 is then dispensed through fluid dispenser 312.

FIG. 5 illustrates a cross-sectional view of a thermoelectric cooling unit 500, in accordance with another embodiment of the present disclosure.

Thermoelectric cooling unit 500 comprises thermoelectric devices 102, metal standoffs 104, cold sink 106, hot sink 108, heat pipes 502, condenser fins 114, fan 116, and a hot sink fan 504.

In thermoelectric cooling unit 500, thermoelectric devices 102, heat pipes 502, cold sink 106 and hot sink 108 are in a vertical orientation. Cold sink 106 is in thermal contact with the cold fluid. The cold side of thermoelectric devices 102 is attached to metal standoffs 104. The hot side of thermoelectric devices 102 is attached to heat pipes 502 and hot sink 108. Hot sink fan 504 is attached in close proximity to hot sink 108 to dissipate heat to the ambient. When thermoelectric devices 102 are switched ON, cold sink 106 collects heat from the cold fluid (not shown in the figure). The heat rejected by the thermoelectric devices 102 is transferred to the ambient by two paths. One heat rejection path comprises hot sink 108 in combination with hot sink fan 504. The other heat rejection path comprises heat pipes 502. A working fluid present in heat pipes 502 transfers heat to condenser fins 114. Fan 116 facilitates dissipation of heat from condenser fins 114 to the ambient. The total heat rejected to the ambient (Q_totai) is a sum of two parameters, electrical energy consumed by thermoelectric devices 502 (Qeiecwcai) and the heat extracted from the cold fluid (Q_∞oiing), given by:

Qtotal ⁼ Qelectrical ⁺ Qcooling 0) The conductance (Ktotai) of thermoelectric cooling unit 500 is a sum of two factors, conductance of heat pipes 510 (KHP) and conductance of hot sink 504 (Khotsink). In other terms,

Ktotai ⁼ KHP ⁺ Khotsink (2)

Also, T(TEC _not side) - T(Ambient) = AT_HS = Qtotai / Kt_otai (3)

Where,

T(TEC hot side) is the temperature of the hot side of thermoelectric devices 502; T(Ambient) is the ambient temperature; and

ATHS is the temperature differential across thermoelectric devices 502. Hence, Ktotai is always greater than KHP. Further, ATHS (with hot sink 108) is less than AT_Hs (without hot sink 108). As temperature differential across thermoelectric devices 502 is reduced, efficiency of thermoelectric cooling unit 500 increases.

FIG. 6 illustrates a cross-sectional view of a thermoelectric cooling apparatus 600, in accordance with another embodiment of the present disclosure. Thermoelectric cooling apparatus 600 comprises a first container 602, a second container 604, cold sink 106, metal standoffs 104, thermoelectric devices 102, hot sink 108, heat pipes 606, condenser fins 1 14, and fan 1 16.

First container 602 contains cold fluid 310. Cold sink 106 is in contact with cold fluid 310. Metal standoffs 104 are present between cold sink 106 and the cold side of thermoelectric devices 102. The hot side of thermoelectric devices 102 is attached to hot sink 108 and the first end of heat pipes 606. Hot sink 108 is in contact with warm fluid 308, which is present in second container 604. The second end of heat pipes 606 is connected to condenser fins 114. Fan 116 is connected to condenser fins 114.

When thermoelectric devices 102 are switched ON, heat from cold fluid 310 is transferred through cold sink 106 and metal standoffs 104 to the hot side of

thermoelectric devices 102. Heat from the hot side of thermoelectric devices 102 is conducted through two components - hot sink 108 and heat pipes 606. Hot sink 108 transfers the heat to second container 604 that contains warm fluid 308. In an

embodiment of the present disclosure, an assembly of second container 604 and warm fluid 308 act as a thermal capacitor. In another embodiment of the present disclosure, warm fluid 308 contains encapsulated phase change materials which maintain a constant temperature of the fluid 308. Further, heat from heat pipes 606 is transferred to condenser fins 114 by a working fluid (not shown in the figure) present in heat pipes 606. Fan 116 facilitates the dissipation of the heat from condenser fins 114 to the ambient. During operation of thermoelectric cooling apparatus 600, heat transferred while cooling cold fluid 310 is given by Qcooiing, which is equal to the amount of heat transferred during an initial transient stage process, Qtransient-cooiing-

A total amount of heat (Qtotai) transferred by thermoelectric cooling apparatus 600 is given by, Qtotai ⁼ Qelectrical ⁺ Qcooiing (4)

Where,

Qeiectricai is the electrical energy consumed by thermoelectric devices 102.

The total amount of heat extracted from first container 602 is given by,

Qtotai - QHP ⁺ Qcapacttor (5)

Where,

QHP is the amount of heat transferred to heat pipes 606 and

Qcapacitor is the amount of heat transferred to second container 604.

Further, Qcapacitor ⁼ ΓΠ Ccapadtor ATcapacitor (^)

Where, m = mass of second container 604 with warm fluid 308;

Ccapadtor is specific heat of the assembly of second container 604 and warm fluid 308; and

ATcapadtor '^s temperature increase in the assembly of second container 604 and warm fluid 308.

During a transient stage of removal of heat from cold fluid 310, ATcapadtor increases proportionally with time, in an embodiment of the present invention. After the transient stage of transferring heat from cold fluid 310 (Qtransient-cooiing), the amount of heat removed from cold fluid 310 attains a steady state amount of heat (Qsteady state), which is desirable to maintain cold fluid 310 in a desired temperature range. Since Qsteady state is less than Qtransient-cooiing, ΔΤ_∞ρ₃αΐοΓ decreases close to the ambient during steady state operation. In an embodiment of the present disclosure, a pulse width modulated (PWM) controller is used to control electrical energy supplied to thermoelectric devices 102 and reduce the magnitude of Qeiectncai- Consequently, the total amount of heat (Q_totai ) rejected by thermoelectric cooling apparatus 600 is reduced to the amount of heat rejected during the steady state, Qtotai - Qtotai ⁼ QHP + Qcapacitor (7)

The total amount of heat transferred by thermoelectric cooling apparatus 600 during the steady state (Q_totai^s) is less than the total amount of heat rejected by thermoelectric cooling apparatus 600 (Qtotai).

Thermoelectric devices 102 should always be switched ON to prevent a back flow of heat from second container 604 containing warm fluid 308 to cold fluid 310 present in first container 602. Hence, Qeiectncai never becomes zero (Qeiewcai≠ 0) during the steady state heat transfer. FIG. 7 illustrates a cross-sectional view of a thermoelectric cooling apparatus 700, in accordance with yet another embodiment of the present disclosure.

In addition to the components explained in conjunction with thermoelectric cooling apparatus 600, thermoelectric cooling apparatus 700 comprises a thermal diode 702. Thermal diode 702 is positioned between the hot side of thermoelectric devices 102 and heat pipes 606.

When thermoelectric devices 102 are switched ON, heat from cold fluid 310 is transferred to cold sink 106. Thermoelectric devices 102 transfer the heat from cold sink 106 to the hot side of thermoelectric devices 102. Thermal diode 702 conducts heat from the hot side of thermoelectric devices 102 to hot sink 108 and heat pipes 606. Further, the thermal diode 702 also prevents the back flow of heat from heat pipes 606 and hot sink 108. In an embodiment of the present disclosure, thermal diode 702 is a vapor diode.

In an embodiment of the present disclosure, thermoelectric devices 102 are switched OFF after the completion of the transient stage (initial period of cooling cold fluid 310 up to a desired temperature). PWM controller is configured to switch OFF the thermoelectric device 102 when the transient stage is completed. Further, the PWM controller is also configured to switch ON the thermoelectric device 102 when the cooling phase is in the transient stage. As stated above, thermal diode 702 prevents the back flow of heat from heat pipes 606 and hot sink 108. Hence, when the thermal diode 702 is used with the PWM controller, the electrical power consumed by thermoelectric cooling apparatus 700 (Qeiectricai) is reduced. This implies that when a desired temperature is achieved in cold fluid 310, thermoelectric devices 102 can be switched OFF. When heat leakage (Qi_eakage) is equal to zero, electrical energy utilized by thermoelectric cooling apparatus 700 is zero. Thus, after reaching a steady state temperature, electrical energy utilized by thermoelectric cooling apparatus 700 (Qtotai-ss) at the steady state will be approximately equal to zero. This can be illustrated by the following equation: When, Qieakage = 0; Qeiectricai = 0 From equation (7),

Since, Q_totai-ss is nearly equal to zero,

QHP ^=— Qcapadtor .

Hence, when thermoelectric devices 102 are switched OFF, the thermal capacitor assembly of second container 604 and warm fluid 308) is discharged faster by heat pipes.

In an embodiment of the present disclosure, second container 604 containing warm fluid 308 is replaced with a phase change material. In another embodiment, an encapsulated phase change material can be added to warm fluid 308. FIG. 8 illustrates a cross-sectional view of a thermoelectric cooling apparatus

800, in accordance with yet another embodiment of the present disclosure.

Thermoelectric cooling apparatus 800 comprises top container 304, bottom container 302, a thermoelectric device 802, a metal standoff 804, a heat pipe 803, a first end 806 of heat pipe 803, a diode section 808 of heat pipe 803, condenser fins 114, fan 116, a second end 810 of heat pipe 803, a fin array 812 and cold sink 106.

Thermoelectric device 802 is present at the bottom portion of bottom container 302. Thermoelectric device 802 comprises a hot side and a cold side. The cold side of thermoelectric device 802 is attached to cold sink 106 through metal standoff 804.

Further, the hot side of thermoelectric device 802 is attached to first end 806 of heat pipe 803. Diode section 808 is present between first end 806 and second end 810 of heat pipe 803. Diode section 808 prevents conduction of heat from second end 810 to first end 806 of heat pipe 803. Condenser fins 114 and fin array 812 are connected to second end 810 of heat pipe 803. Fin array 812 is in contact with warm fluid 308 of top container 304 to dissipate heat to warm fluid 308. Further, fan 116 is attached in close proximity to condenser fins 114. Condenser fins 114 and fan 116 dissipate the heat to the ambient.

When thermoelectric device 802 is switched ON, it absorbs heat from cold fluid 310 that is collected by the cold sink 106. Heat from cold sink 106 is conducted to thermoelectric device 802 through metal standoff 804. Thermoelectric device 802 dissipates the heat to the hot side. Heat pipe 803 present at the hot side of thermoelectric device 802 absorbs the heat. Heat pipe 803 transfers the heat to condenser fins 114 and fin array 812. A first portion of the heat absorbed by heat pipe 803 is dissipated by condenser fins 114 to the ambient. Fan 116 facilitates the dissipation of heat from condenser fins 114. Further, a second portion of heat absorbed by heat pipe 803 is dissipated to warm fluid 308 through fin array 812.

In an embodiment of the present disclosure, warm fluid 308 and cold fluid 310 are water. Thus, in an embodiment of the present disclosure, thermoelectric cooling apparatus 800 is a water cooler.

FIG. 9 illustrates a cross-sectional view of a thermoelectric cooling apparatus 900, in accordance with yet another embodiment of the present disclosure.

Thermoelectric cooling apparatus 900 comprises a container 902, thermoelectric devices 102, metal standoffs 104, cold sinks 106, a fluid 904, a heat pipe 906, an insulation 908, a lid 910, an insulation section 912, condenser fins 114 and fan 1 16.

Container 902 contains fluid 904 to be cooled. Cold sinks 106 are in contact with fluid 904 so that cold sinks 106 can absorb heat from fluid 904. As discussed in conjunction with FIG. 1 , the cold side of thermoelectric devices 102 is attached to cold sinks 106. Further, the hot side of thermoelectric devices 102 is attached to heat pipe 906. Heat pipe 906 comprises insulation section 912 between the first end and the second end of heat pipe 906 to prevent the conduction of heat from the second end to the first end of heat pipe 906. Thus, insulation section 912 prevents a backflow of heat from heat pipe 906. Insulation 908 encloses heat pipe 906 and cold sinks 106, and prevents convective heat transfer between fluid 904 and heat pipe 906.

When thermoelectric devices 102 are switched ON, they absorb heat at the cold side and reject the heat at the hot side. Heat from fluid 904 is transferred to cold sinks 106. Themrioelectric devices 102 collect heat from cold sinks 106 through metal standoffs 104. Thermoelectric devices 102 transfer heat to the hot side of thermoelectric devices 102. Heat pipe 906 conducts the heat from the hot side of thermoelectric devices 102 to condenser fins 114. Insulation 908 encloses heat pipe 906 and cold sinks 106 to prevent thermal leakage from heat pipe 906 to cold sinks 106. Lid 910 encloses container 902 to prevent heat leakage from the ambient to thermoelectric cooling apparatus 900. In an embodiment of the present disclosure, lid 910 is made of materials such as plastic. Condenser fins 114 and fan 116 are configured to dissipate heat from pipe 906 to the ambient.

An advantage of thermoelectric cooling apparatus 900 is that an assembly comprising cold sinks 106, thermoelectric devices 102, metal standoffs 104, heat pipe 906, insulation 908, lid 910, condenser fins 114 and fan 116 can be easily assembled with any container on which the lid 910 can be fitted. Further, thermoelectric cooling apparatus 900 can be used as a portable cooling apparatus very effectively.

FIG. 10 illustrates a cross-sectional view of a thermoelectric cooling apparatus 1000, in accordance with yet another embodiment of the present disclosure.

Thermoelectric cooling apparatus 1000 comprises a chamber 1002, lid 910, thermoelectric device 102, metal standoff 104, cold sink 106, a back plate 1006, an evaporator plate 1004, heat pipes 1008, condenser fins 114, and fan 116.

Chamber 1002 comprises fluid 904. Cold sink 106 is in contact with fluid 904. The hot side of thermoelectric device 102 is attached to evaporator plate 1004. Further, the cold side of thermoelectric device 102 is attached to metal standoff 104. Metal standoff 104 is attached to cold sink 106. In an embodiment of the present disclosure, insulation 908 is configured to prevent heat transfer from thermoelectric device 102, heat pipes 1008, and evaporator plate 1004 to fluid 904. Evaporator plate 1004 is attached to the first end of heat pipes 1008. A second end of heat pipes 1008 is attached to condenser fins 114, which are in close proximity to fan 116. In an embodiment of the present disclosure, heat pipes 1008 provide unidirectional heat flow from thermoelectric device 102. Grommets 1010 facilitate the attachment of an assembly of thermoelectric device 102, metal standoff 104 and cold sink 106 to back plate 1006.

When thermoelectric cooling apparatus 1000 is switched ON, thermoelectric device 102 absorbs heat at the cold side and rejects heat at the hot side. Heat absorbed from fluid 904 is transferred to cold sink 106. Further, heat from cold sink 106 is transferred to the hot side of thermoelectric device 102 through metal standoff 104. Metal standoff 104 present between cold sink 106 and thermoelectric device 102 is configured to reduce heat leakage between the hot side of thermoelectric device 102 and cold sink 106. Evaporator plate 1004 collects heat from the hot side of

thermoelectric device 102. Heat from evaporator plate 1004 is transferred to condenser fins 114 through heat pipes 1008. Fan 116 facilitates dissipation of heat from condenser fins 114 to the ambient. In an embodiment, an assembly of evaporator plate 1004, metal standoff 104, thermoelectric device 102 and heat pipes 1008 are encased with thermal insulation to prevent convective heat transfer between fluid 904 and the assembly.

Further, the electrical wiring to the thermoelectric modules is also encased in the same insulation.

FIG. 11 illustrates a cross-sectional view of a thermoelectric cooling apparatus 1100, in accordance with yet another embodiment of the present disclosure.

Thermoelectric cooling apparatus 1100 comprises the elements mentioned in conjunction with FIG. 10— chamber 1002, thermoelectric devices 102, metal standoffs 104, cold sinks 106, evaporator plates 1004, heat pipes 1008, lid 910, condenser fins 114, fan 116, and insulation 1010. Thermoelectric cooling apparatus 1100 provides an apparatus symmetric with respect to heat pipes 1008.

Cold sinks 106 are in contact with fluid 904. In an embodiment of the present disclosure, fluid 904 is water. Evaporator plates 1004 are attached to the first end of heat pipes 1008. Further, a second side of evaporator plates 1004 is attached to thermoelectric devices 102. Metal standoffs 104 are present between thermoelectric devices 102 and cold sinks 106. The second end of heat pipes 1008 is attached to condenser fins 114. In an embodiment of the present disclosure, heat pipes 1008 are attached to condenser fins 114 using an epoxy solution. In another embodiment of the present disclosure, heat pipes 1008 are attached through an interference fit to

condenser fins 114. Fan 116 is in close proximity to condenser fins 1 14. In an

embodiment of the present disclosure, insulation 908 is configured to prevent heat transfer from thermoelectric device 102, heat pipes 1008, and evaporator plate 1004 to fluid 904. Thermoelectric devices 102 are configured to transfer heat from fluid 904 to heat pipes 1008. A convective heat transfer takes place between fluid 904 and cold sinks 106 when thermoelectric cooling apparatus 1100 is switched ON. Thermoelectric devices 102 absorb heat at the cold side and reject heat at the hot side. Heat absorbed from fluid 904 is transferred to cold sinks 106 through metal standoffs 104. From the first end of heat pipes 1008, heat is transferred to condenser fins 114 with the help of a working fluid present in heat pipes 1008. Insulation 1010 prevents the backflow of heat from the hot side of thermoelectric devices102 and evaporator plates 1004 to fluid 904.

Heat pipes 1008 conduct heat from evaporator plates 1004. Condenser fins 114 facilitate the transfer of heat from heat pipes 1008 to the ambient. Further, fan 116 facilitates dissipation of heat from condenser fins 1 14 to the ambient.

FIG. 12 illustrates a cross-sectional view of a thermoelectric cooling apparatus 1200, in accordance with an embodiment of the present disclosure.

Thermoelectric cooling apparatus 1200 comprises a container 1202, an insulation layer 1204, a fluid inlet 1206, a separator 1208, an outlet tube 1210, cold sink 106, metal standoff 104, thermoelectric devices 102, heat pipes 110, condenser fins 114, and fan 116.

Container 1202 stores a fluid 1212 to be cooled by thermoelectric device 102. Cold sink 106 is in thermal contact with fluid 1212. Separator 1208 is located between fluid 1212 and cold sink 106. In an embodiment of the present disclosure, separator 1208 is configured to facilitate in directing fluid 1212 entering through fluid inlet 1206 to make a contact with cold sink 106. In yet another embodiment of the present disclosure, separator 1208 is present along a length of container 1202. Further, the movement of fluid 1212 through cold sink 106 may facilitate removal of a motionless boundary layer (thermal) which may be present at the fins of cold sink 106. As a result, cold sink 106 may be more efficient in removing heat from fluid 1212.Cold sink 106 is attached to a first side of metal standoff 104. A second side of metal standoff 104 is attached to the cold side of thermoelectric devices 102. The hot side of thermoelectric devices 102 is attached to the first end of heat pipes 116. The second end of heat pipes 116 is attached to condenser fins 114. Fan 116 is thermally coupled to condenser fins 114 to dissipate heat.

When thermoelectric device 102 is switched ON, the thermal transfer starts from fluid 1212 to cold sink 106. Thermoelectric devices 102 transfer heat from cold sink 106 to heat pipes 110. Heat from the second end of heat pipes 110 is dissipated to the ambient through condenser fins 114 and fan 116. A bottom region of container 1202 comprises fluid 1212 which is cold. This fluid is dispensed from the container 1202 through outlet tube 1210 on demand. A dispenser (not shown in figure) can be placed at the end of outlet tube 1210 to control the flow of fluid 1212. Further, when fluid 1212 is stored in container 1202, insulation layer 1204 prevents heat leakage from the ambient.

FIG. 13 illustrates a cross-sectional view of a thermoelectric cooling apparatus 1300, in accordance with an embodiment of the present disclosure.

Thermoelectric cooling apparatus 1300 comprises a container 1302, fluid 1212 to be cooled, a cold sink 1304, metal standoff 104, thermoelectric device 102, a heat pipe - heat sink assembly 1306, and fan 116. In an embodiment of the present disclosure, container 1302 is enclosed by an insulation material (not shown in figure).

The direction of flow of fluid 1212 into container 1302 is denoted by arrow 1308. Cold sink 1304 is in contact with fluid 1212. One of the sides of cold sink 1304 is attached to the first side of metal standoff 104. The second side of metal standoff 104 is attached to the cold side of thermoelectric devices 102. The hot side of thermoelectric devices 102 is attached to heat pipe - heat sink assembly 1306. Fan 116 is thermally coupled to heat pipe - heat sink assembly 1306. For example, in the present

embodiment, thermoelectric devices 102 are positioned at the bottom side of the container 1302 to increase the amount of fluid 1212 that contacts cold sink 1304 before being dispensed.

When thermoelectric devices 102 are switched ON, thermoelectric devices 102 start to transfer heat from fluid 1212 to heat pipe - heat sink assembly 1306. Heat from fluid 1212 is conducted by cold sink 1304. In an embodiment of the present disclosure, the length of cold sink 1304 is considerably high compared with cold sinks 106 (refer to FIG. 1 to FIG. 11). The increased length of cold sink 1304 results in greater amount of fluid 1212 to be in contact with cold sink 1301 , thereby creating more uniform cooling.

Further, heat from cold sink 1304 is transferred to the first side of metal standoff 104. Thermoelectric devices 102 transfer heat from the second side of metal standoff 104 to heat pipe - heat sink assembly 1306. In an embodiment of the present disclosure, heat pipe - heat sink assembly 1306 comprises heat pipes 1312 embedded into the metal base of heat pipe - heat sink assembly 1306. Heat pipes 1312 help with better spreading of the heat and reduce the thermal spreading resistance. In another embodiment of the present disclosure, heat pipes 1312 can extend out of heat pipe - heat sink assembly 1306 base and can be inserted into the fins of a heat exchanger. In another embodiment of the present disclosure, heat pipe - heat sink assembly 1306 comprises a thermosyphon. A thermosyphon uses a convective fluid such as alcohol to transfer heat. The convective fluid present in the thermosyphon evaporates initially at a region of contact with a hot surface and condenses later on. This results in the

transportation of heat within the thermosyphon. In yet another embodiment of the present disclosure, heat pipe - heat sink assembly 1306 may be coupled with another convective or conductive heat rejection apparatus. Usage of heat pipe - heat sink assembly 1306 increases heat transfer efficiency of thermoelectric cooling apparatus 1300. Heat from the heat pipe - heat sink assembly 1306 is dissipated to the ambient through fan 116. After cooling, fluid 1212 is dispensed from the bottom of container 1302 as denoted by an arrow 1310. A suitable dispensing mechanism may be used, attached to the bottom of container 1302, to dispense fluid 1212.

FIG. 14 illustrates a cross-sectional view of a thermoelectric cooling apparatus 1400, in accordance with yet another embodiment of the present disclosure.

Apparatus of thermoelectric cooling apparatus 1400 comprises most of the parts in common with thermoelectric cooling apparatus 1200 such as container 1202, fluid 1212, insulation layer 1204, separator 1208, outlet tube 1210, cold sink 106, metal standoff 104, thermoelectric devices 102, and fan 116. However, a combination of parts forming a heat dissipation apparatus (not labeled in FIG. 14) attached to the hot side of thermoelectric device 102 is different. The heat dissipation apparatus is a collective term for a heat spreader 1402, a pump 1404, fins 1406, fan 116, and a convective fluid (not shown in figure). In an embodiment of the present disclosure, the convective fluid is water. Forced convection occurs in the heat dissipation apparatus when fluid flow is induced by pump 1404. Other types of convective fluids can also be used for the transfer of heat from the hot side of thermoelectric device 102.

Thermoelectric devices 102 are configured to transfer heat from fluid 1212 to heat spreader 1402. During functioning of thermoelectric cooling apparatus 1400, heat from fluid 1212 is transferred to cold sink 106. In an embodiment of the present disclosure, separator 1208 is configured to facilitate transfer of heat from fluid 1212 to cold sink 106. Separator 1208 may comprise holes to let fluid 1212 to flow through it. Metal standoff 104 conducts heat from cold sink 106 and transfers to thermoelectric devices 102. Heat from the hot side of thermoelectric devices 102 is transferred using the heat dissipation apparatus. For example, heat spreader 1402 may comprise passages embedded in a plate for transfer of the convective fluid. The convective fluid carries heat from heat spreader to fins 1406. The transportation of the convective fluid in the heat dissipation apparatus may be facilitated by pump 1404. Fan 116 is configured to dissipate heat from fins 1406 to the ambient. In an embodiment of the present disclosure, fan 116 may be a blower fan. Thus, heat from fluid 1212 is removed using thermoelectric cooling

apparatus 1400.

Fluid 1212 cooled by the thermoelectric cooling apparatus 1400 is denser than the warm fluid that is introduced into container 1202. If required, cold fluid 1212 present at the bottom of container 1202 is dispensed from the outlet tube 1210. A dispensing mechanism (not shown in figure) may be included at outlet tube 1210 to control flow of fluid 1212.

FIG. 15 illustrates a cross-sectional view of a cooling apparatus 1500, in

accordance with an embodiment of the present disclosure.

Cooling apparatus 1500 comprises fluid treatment devices 1502, drain tubes 1508, drain tubes 1510 and thermoelectric cooling apparatus 1200. According to the present embodiment, fluid 1212 is purified or treated before it is cooled using thermoelectric cooling apparatus 1200. However, fluid from any physical or chemical treatment apparatus can be channelized for cooling. For example, the treatment apparatus may be reverse osmosis equipment for water or distillation equipment for water/other fluids or the like. According to the present embodiment, treatment devices 1502 comprise treatment chambers 1504, a fluid inlet 1506, a fluid outlet 1508, drain tubes 1510, and a collector tube 1512. Further, thermoelectric cooling apparatus 1200 may include a venting device such as a bubbler or the like present in container 1202 to release an air lock or any trapped bubbles. Arrangement of components in the present embodiment is an example, provided for illustration, and should not be construed as limitations.

Untreated fluid 1212 to be treated is introduced into one of treatment chambers 1504 through fluid inlet 1506. Treatment devices 1502 produce waste fluid or effluents which are removed from treatment chambers 1504 through drain tubes 1510. Collector tube 1512 is configured to collect waste fluid from drain tubes 1510. In an embodiment of the present disclosure, waste fluid from treatment devices 1502 is channelized to cool the hot side of thermoelectric device 102.

Working of thermoelectric cooling apparatus 1200 is explained in detail in conjunction with FIG. 12. Thermoelectric cooling apparatus 1200 is provided for cooling fluid 1212 from treatment devices 1502. Fluid 1212 cooled by thermoelectric cooling apparatus 1200 is dispensed on demand using a dispenser 1514 after cooling.

FIG. 16 illustrates graph 1 depicting variation in input current with time, and graph 2 depicting variation in temperature with time for a thermoelectric cooling apparatus, in accordance with an embodiment of the present disclosure. Graph 1 plots a variation of input current with respect to time during the process of cooling a fluid using a thermoelectric cooling apparatus in accordance with the present embodiment. In graph 1 , time is represented on a horizontal axis 1604 and current is represented on a vertical axis 1602. Curve 1606 represents variation in the current input to the thermoelectric cooling apparatus with time. An optimal current l_opt, denoted by 1608 is utilized to cool the fluid initially. The efficiency of the thermoelectric cooling apparatus is maximized when the optimal current IOPT is passed through it. After a time denoted by a vertical dotted line 1616, a minimum amount of current is passed through the thermoelectric cooling apparatus. A constant magnitude of steady state current denoted by dotted line 1610 is passed through the thermoelectric cooling apparatus to maintain the fluid at a desired temperature range.

Graph 2 shows the performance of a thermoelectric cooling apparatus in accordance with an embodiment of the present invention, and plots the variation in the temperature of the fluid with time during a process of cooling. In Graph 2, time is represented on a horizontal axis 1604, and temperature is represented on a vertical axis 1612. Curve 1614 represents variation of temperature of the fluid with respect to time, and this variation has been indicated by Tc. Temperature of the fluid decreases below set point temperature (Ts) at the time denoted by vertical dotted line 1616. T_s is the target temperature that is to be maintained in the fluid. Curve 1618 represents variation of temperature of the hot side of the

thermoelectric cooling apparatus. Temperature of the hot side of the thermoelectric cooling apparatus reaches a maximum at the time denoted by vertical dotted line 1616, when the thermoelectric cooling apparatus is switched ON.

Current required to cool the fluid initially is at l_opt denoted by 1608. When the thermoelectric cooling apparatus is switched ON, the heat rejected by the cooling apparatus is initially high which results in increased temperature of the hot side. As ΔΤ across the thermoelectric modules increases, COP decreases resulting in lower heat pumping from the fluid. This results in the temperature of the hot side of the

thermoelectric cooling apparatus to saturate to a high value as denoted in 1618 for I = l₀pt- For I = l_opt, the temperature of the fluid is reduced, as denoted by curve 1614. The temperature of the hot side of the thermoelectric cooling apparatus is always higher than an ambient temperature T₀ denoted by a line 1620. Temperature of the hot side of the thermoelectric cooling apparatus is above the ambient temperature T₀. ΔΤ (as labeled in the graph 2) denotes a temperature difference between the hot side temperature of the thermoelectric cooling apparatus and the set point temperature T_s. After the time denoted by vertical dotted line 1616, the thermoelectric cooling apparatus is operated at I = Iss, which is the minimum current required to maintain temperature difference ΔΤ between the hot side temperature of the thermoelectric cooling apparatus and the set point temperature T_s .

FIG. 17 illustrates graph 3 depicting variation in input current with time, and graph 4 depicting variation in temperature with time for a thermoelectric cooling apparatus, in accordance with another embodiment of the present disclosure. Graph 3 depicts variation of current with respect to time during the process of cooling a fluid using a thermoelectric cooling apparatus, in accordance with the present embodiment. A vertical axis 1702 represents current and a horizontal axis 1304 represents time.

Curve 1706 represents variation of current passed through the thermoelectric cooling apparatus with time.

For an initial period of time, the thermoelectric cooling apparatus is powered with an optimal current l_opt which is denoted by 1708. When temperature of the fluid reaches a lower limit of temperature (T_SL), a steady state current denoted by 1710 is passed through the thermoelectric cooling apparatus to maintain a set temperature of the fluid. The minimal steady state current Iss is maintained through current or voltage biasing.

Graph 4 shows the performance of the thermoelectric cooling apparatus in accordance with an embodiment of the present invention, and plots the variation in the temperature of the fluid with time during a process of cooling. Graph 4 also depicts variation of temperature of the hot side of the thermoelectric cooling apparatus with respect to time.

A vertical axis 1712 represents temperature of the hot side of the thermoelectric cooling apparatus, and a horizontal axis 1704 represents time. A curve 1714 represents variation of temperature of the hot side of the thermoelectric cooling apparatus. Further, a curve 1716 represents variation of temperature of the fluid to be cooled after switching ON the thermoelectric cooling apparatus. A dotted line 1718 represents the ambient temperature (T₀). A dotted line 1720 represents an upper limit (Tsu) of temperature of the fluid. A dotted line 1722 represents a lower limit (TSL) of temperature of the fluid. The difference between the ambient temperature (T₀) and lower limit (TSL) of temperature of the fluid is defined as (ATsTEc), represented by arrow 1724.

The thermoelectric cooling apparatus is switched ON and optimal current l_opt is passed until a time denoted by 1726, when the temperature of fluid reaches TSL-

Thereafter, steady state current , which is denoted by curve 1710 is passed through the thermoelectric cooling apparatus to provide minimum amount of cooling that would offset heat leakage from the hot side of the cooling apparatus. Due to small heat leakage through the insulated walls of fluid enclosure, the temperature of the fluid starts increasing, which is denoted at curve 1728. After the temperature of the thermoelectric cooling apparatus rises to Tsu, the current being passed through the thermoelectric apparatus is again increased to l_opt so that the temperature of the fluid starts decreasing again. The temperature of the hot side of the thermoelectric cooling apparatus is close to ambient temperature T₀, denoted by a curve 1730. The cycle of variation of the current through the thermoelectric cooling apparatus is continued to maintain the fluid within the desired temperature range.

FIG. 18 illustrates graph 5 depicting variation in input current with time, and graph 6 depicting variation in temperature with time for a thermoelectric cooling apparatus in accordance with yet another embodiment of the present disclosure. This is in contrast to FIG. 16 and FIG. 17, where the cooling apparatus was operated at a constant current l_opt during the ON phase.

Graph 5 depicts variation of input current with respect to time during the process of cooling a fluid using a thermoelectric cooling apparatus, in accordance with the present embodiment. In graph 5, current is represented on a vertical axis 1802 and time is represented on a horizontal axis 1804. A curve 1806 depicts variation of current for an initial period of time (represented as a point 1808), when the thermoelectric cooling apparatus is kept switched ON. According to curve 1806, the magnitude of current reduces gradually till point 1808. Further, during this period, the magnitude of current given by the equation below is passed through the thermoelectric cooling apparatus: = r(T_w -T_s) (8)

The magnitude of current is proportional to the temperature difference between the temperature of the fluid at any given time(T_w) and the set temperature (T_s). γ is the constant of proportionality. The value of current at point 1808 is nearly equal to zero. Due to heat leakage from the ambient, the temperature of the fluid starts rising. A dotted line 1812 represents a point on axis 1804 when the temperature of the fluid becomes Tsu and the thermoelectric cooling apparatus is switched ON. At line 1812, there is an abrupt increase in the consumption of current. A curve 1814 depicts the variation of current when the thermoelectric cooling apparatus is switched ON again. A curve 1816 depicts a stage where consumption of current becomes nearly zero and when the thermoelectric cooling apparatus gets switched OFF.

Graph 6 shows the performance of a thermoelectric cooling device in accordance with an embodiment of the present invention, and plots the variation in the temperature of the fluid with time during a process of cooling.

Graph 6 depicts a variation of temperature of a hot side and a cold side of the thermoelectric cooling apparatus with respect to time. In graph 6, temperature is represented by a vertical axis 1818 and time is represented by horizontal axis 1804. Variation of temperature of hot side of the thermoelectric cooling apparatus is

represented by a curve 1820 and variation of temperature of the cold side of the thermoelectric cooling apparatus is represented by a curve 1826. According to curve 1820, the temperature of the hot side of the thermoelectric cooling apparatus initially increases and as the current decreases, the hot side temperature decreases to a value near the ambient temperature (T₀), which is represented by a line 1824. When the thermoelectric cooling apparatus is switched OFF, the temperature of the hot side of the thermoelectric cooling apparatus is equal to the temperature of the ambient (To). A curve 1826 represents variation of temperature of a cold side of the thermoelectric cooling apparatus. According to curve 1826, the temperature of the cold side of the thermoelectric cooling apparatus reduces initially up to the time

corresponding to line 1808 when the thermoelectric cooling apparatus is switched ON. At time represented by line 1808, the temperature of the fluid reaches TSL and the thermoelectric cooling apparatus is switched OFF. As shown in curve 1828, the temperature of the cold side increases from a lower temperature of the cold side (T_SL), represented by a line 1830 to a higher temperature of the cold side (Tsu). When the thermoelectric cooling apparatus is kept switched OFF, temperature of the fluid rises, as shown at curve 1828. As the temperature reaches Tsu, the thermoelectric cooling apparatus is switched ON at a time represented by line 1812. The temperature of the cold side of the thermoelectric cooling apparatus starts decreasing again as shown by curve 1834. The temperature is allowed to decrease to a level TSL, represented by line 1830. At time represented by line 1836, the thermoelectric cooling apparatus is switched OFF again resulting in increase of temperature of the fluid, represented by a curve 1838. The cycle of variation of the current through the thermoelectric cooling apparatus is continued to maintain the fluid within the desired temperature range.

FIG. 19 illustrates a flow chart 1900 representing a method of operation of a thermoelectric cooling apparatus. The method starts at step 1902. At step 1904, the type of current that is provided for the thermoelectric cooling apparatus is checked. If the current supplied is of

Alternating Current (AC) type, it is converted to Direct Current (DC). A user-selected mode is verified at step 1908. If the mode is high power mode, then high power mode parameters are implemented at step 1910. Subsequently, at step 1918, voltage supplied to the thermoelectric cooling apparatus is set at maximum voltage (V_max). If the selected mode is not the high power mode, then efficiency mode parameters are implemented at step 1912. The efficiency mode parameters relate to the efficient current biasing of the thermoelectric module. At step 1914, after a predetermined amount of time, the temperature of fluid (T_w) is verified to be within a desired range. If yes, then the voltage is set to minimum voltage (V_min) at step 1916. For example, the minimum voltage implemented in the thermoelectric cooling apparatus, according to the present embodiment may be sufficient to maintain water in the desired temperature range. If not, at step 1918, the voltage is set to maximum voltage (V_max). Subsequently, the fluid is cooled in the desired mode at step 1920. The method stops at step 1922. The above mentioned control flowchart may be integrated in a printed circuit board with Integrated Circuits (ICs) for temperature sensing and power switches or any other means as suitable.

While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; one or more heat pipes comprising a first end and a second end, the first end being attached to the hot side of the one or more thermoelectric devices, wherein the one or more heat pipes are configured to assist in transfer of heat from the hot side of the one or more thermoelectric devices to an ambient; and condenser fins attached to the second end of the one or more heat pipes, the condenser fins configured to assist in dissipating heat from the second end of the one or more heat pipes to the ambient.

2. The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprises a hot sink attached to the first end of the one or more heat pipes, wherein the hot sink is configured to assist in dissipating heat from the first end of the one or more heat pipes.

3. The thermoelectric cooling apparatus in accordance with claim 2, the

thermoelectric cooling apparatus further comprises a plurality of screws, wherein the plurality of screws is configured to facilitate attachment of the hot sink and the cold sink.

4. The thermoelectric cooling apparatus in accordance with claim 2, the thermoelectric cooling apparatus further comprising a plurality of grommets, wherein the plurality of grommets is configured to prevent heat conduction from the hot sink to the cold sink.

5. The thermoelectric cooling apparatus in accordance with claim 2, the

thermoelectric cooling apparatus further comprising a hot sink fan thermally coupled to the hot sink, wherein the fan is configured to dissipate heat from the hot sink to the ambient.

6. The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprising a fan thermally coupled to the condenser fins, wherein the fan is configured to dissipate heat from the condenser fins to the ambient.

7. The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprising an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices.

8. The thermoelectric cooling apparatus in accordance with claim 1 , wherein the cold sink comprises at least one of anodized aluminum, copper and nickel.

9. The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprising an insulation material, wherein the insulation material is configured to fill gaps between elements of the thermoelectric cooling apparatus.

10. The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprising a thermal diode positioned between the hot side of the one or more thermoelectric devices and the one or more heat pipes, wherein the thermal diode is configured for unidirectional heat transfer.

11.The thermoelectric cooling apparatus in accordance with claim 1 , the

thermoelectric cooling apparatus further comprising one or more containers containing the fluid, wherein one of the one or more containers is configured to function as a thermal capacitor.

12. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices is configured to cool a fluid; a cold sink attached to the cold side of the one or more thermoelectric devices, the cold sink being configured to transfer heat from the fluid to the one or more thermoelectric devices; one or more diodic heat pipes comprising a first end and a second end, the first end of one or more diodic heat pipes being attached to the hot side of the one or more thermoelectric devices, wherein the one or more diodic heat pipes are configured to facilitate transfer heat from the hot side of the one or more thermoelectric devices to an ambient; and a fin array attached to the second end of the one or more heat pipes, wherein the fin array is configured to transfer heat from the second end of the one or more heat pipes.

13. The thermoelectric cooling apparatus in accordance with claim 12, the

thermoelectric cooling apparatus further comprising condenser fins attached to the one or more heat pipes, wherein the condenser fins are configured to assist in dissipation of heat from the one or more heat pipes.

14. The thermoelectric cooling apparatus in accordance with claim 13, the

15. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices is configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; one or more cold sinks attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and

one or more heat pipes comprising a first end and a second end, the first end of the one or more heat pipes being attached to the hot side of the one or more

thermoelectric devices, wherein the one or more heat pipes are configured to assist in dissipating heat from the hot side of the one or more thermoelectric devices to the ambient.

16. The thermoelectric cooling apparatus in accordance with claim 15, the

thermoelectric cooling apparatus further comprising condenser fins and a fan, the condenser fins being in close proximity to the second end of the one or more heat pipes, wherein the condenser fins and the fan are configured to dissipate heat from the one or more heat pipes to the ambient.

17. The thermoelectric cooling apparatus in accordance with claim 15, wherein the one or more heat pipes further comprise an insulated section to prevent the conduction of heat from the second end to the first end of the one or more heat pipes.

18. The thermoelectric cooling apparatus in accordance with claim 15, the

thermoelectric cooling apparatus further comprising an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the

evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices.

19. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and

a separator configured to direct the fluid towards the cold sink.

20. The thermoelectric cooling apparatus in accordance with claim 19, the

thermoelectric cooling apparatus further comprising a convective heat dissipation apparatus thermally coupled to the hot side of the one or more thermoelectric devices, the convective heat dissipation apparatus being configured to remove heat from the hot side of the one or more thermoelectric devices to the ambient, wherein the convective heat dissipation apparatus comprises a convective fluid for heat transportation, a heat spreader, a pump, fins and a fan.

21. The thermoelectric cooling apparatus in accordance with claim 19, wherein the separator comprises a plurality of pores.

22. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and a heat pipe-heat sink assembly attached to the hot side of the one or more thermoelectric devices, wherein the heat pipe-heat sink assembly is configured to dissipate heat from the hot side of the one or more thermoelectric devices to the ambient.

23. The thermoelectric cooling apparatus in accordance with claim 22, the

thermoelectric cooling apparatus further comprising a fan thermally coupled to the heat pipe-heat sink assembly, wherein the fan is configured to dissipate heat from the heat pipe-heat sink assembly to the ambient.

24. A method of cooling a fluid by using a thermoelectric apparatus, comprising: operating the thermoelectric apparatus at optimum conditions when the

temperature of the fluid is not within a predetermined temperature range; determining the temperature of the fluid at predetermined time intervals; and operating the thermoelectric apparatus at steady state conditions when the temperature of the fluid is within the predetermined temperature range.

25. The method according to claim 24, wherein operating the thermoelectric cooling apparatus at optimum conditions includes supplying an optimum current (l_opt) to the thermoelectric cooling apparatus.

26. The method according to claim 24^ wherein operating the thermoelectric apparatus at steady state conditions includes supplying a steady state current (Iss) to the thermoelectric apparatus.

27. A method of operating a thermoelectric cooling apparatus for cooling a fluid, the method comprising: selecting at least one mode of operation from a plurality of modes of operation for the thermoelectric cooling apparatus; and supplying maximum voltage (V_max) or minimum voltage (V_min) to the

thermoelectric cooling apparatus based on the selected mode of operation.

28. The method in accordance with claim 27, wherein the plurality of modes includes a high power mode and a power efficiency mode.

29. The method in accordance with claim 28, the method further comprising switching from V_minto Vmax when the temperature of the fluid is greater than a predetermined temperature (T_w).