AU2020286146A1

AU2020286146A1 - System and apparatus for energy reclaimation

Info

Publication number: AU2020286146A1
Application number: AU2020286146A
Authority: AU
Inventors: Chee Hien MOK
Original assignee: Zog Eng Sdn Bhd
Current assignee: Zog Engineering Sdn Bhd
Priority date: 2019-05-27
Filing date: 2020-05-20
Publication date: 2022-01-06
Also published as: WO2020242289A1; CN217274955U

Abstract

The present invention discloses an evaporator (1) for use within a cooling sub-system (2) of an energy reclaim system, the evaporator (1) being adapted to receive a refrigerant liquid and expand the refrigerant into a gaseous and a liquid phase, a heat exchanger means (3) being provided to cause the refrigerant liquid to boil at low pressure while extracting heat from a fluid heat exchange medium and an integral subcooling means (4) to further superheat the refrigerant vapor for supply to a compressor (5) of the energy reclaim system.

Description

SYSTEM AND APPARATUS FOR ENERGY RECLAIMATION

FIELD OF INVENTION The invention relates to a system and apparatus for energy reclamation. More particularly, the invention relates to an energy reclamation system for a cooling system and a chiller system.

BACKGROUND OF THE INVENTION

In the present, government agencies and the industries are moving towards energy efficient equipment in their effort to maintain low energy intensity buildings, preserve energy resources, reduce carbon footprint, reduce greenhouse gas emission, reduce global warming and other environmental impacts. Stringent regulation is imposed on the minimum energy requirement and energy rating of major energy related equipment, such as the air conditioning and heating equipment, which consume most of the generated power. In the application of a cooling system, its compressor requires higher energy to compress refrigerant discharged from an evaporator when the refrigerant is not in a desirable condition, for example, a mixture of gaseous and refrigerant liquid. Therefore, innovative solution and breakthrough technology are required in the global challenge on energy efficiency.

There are a few patented technologies over the prior art relating to the heat reclamation system and apparatus. US8353175B2 discloses a system comprising a plurality of rooftop HVAC units having a centralized refrigeration unit is described along with a method for retrofitting existing independent HVAC units into the described system. The resulting multi-unit system offers increased efficiency and reliability over independently operating HVAC units. Another system and apparatus are disclosed in W02008079829A2. This teaching, provides a cooling system for providing conditioned air to a facility includes a chiller or other cooling subsystem, a cooling tower subsystem and one or more air handling units or process cooling units. The cooling subsystem may advantageously include one or more chillers (e.g., variable speed chillers, constant speed chillers, absorption chillers, etc.) and chilled fluid pumps. The cooling tower subsystem includes one or more cooling tower units and condenser fluid pumps. In some implementations, the air handling unit has a cooling coil and a variable volume fan. In some implementations, direct expansion (DX) cooling systems comprise compressors, evaporators and air-cooled, water-cooled or evaporatively-cooled condensing systems. Such systems can be controlled to reduce energy waste, improve occupant comfort and/or improve the thermal characteristics of the process cooling unit. The cooling system further comprises a control system which is configured to evaluate a cooling load value at the air handling unit and use the cooling load value to calculate at least one operational setpoint. The operational setpoint may advantageously be selected to improve the energy efficiency of the overall cooling system.

However, the system disclosed in US8353175B2 and W02008079829A2 does not suggest a teaching to incorporate both the cooling system and chiller system for energy reclamation.

Accordingly, it would be desirable to provide a system that reduces energy consumption of the cooling system and chiller system through energy reclamation. This invention provides such a system and apparatus.

SUMMARY OF INVENTION

One objective of the invention is to provide an energy reclamation system for enhancing the energy efficiency of a chiller or a refrigeration system, by reducing the power consumption of the compressor without compromising the ultimate cooling capacity of the system.

In a first aspect of the invention, there is provided an evaporator for use within a cooling sub-system of an energy reclaim system, the evaporator being adapted to receive a refrigerant liquid and expand the refrigerant into a gaseous and a liquid phase, a heat exchanger means being provided to cause the refrigerant liquid to boil at low pressure while extracting heat from a fluid heat exchange medium and an integral subcooling means to further superheat the refrigerant vapor for supply to a compressor of the energy reclaim system.

In this aspect of the invention, the evaporator may comprise a first section and a second section for housing the integral subcooling means and the heat exchanger means respectively.

In this aspect of the invention, the integral subcooling means may comprises an inlet tube for receiving the refrigerant liquid from a condenser and an outlet tube for discharging the refrigerant liquid to an expansion valve.

In this aspect of the invention, the expansion valve may expand the received refrigerant liquid into a gaseous and a liquid phase.

In this aspect of the invention, the inlet tube and the outlet tube may be disposed horizontally within the first section, in which the inlet tube is disposed at a higher level than the outlet tube.

In this aspect of the invention, the heat exchanger means may comprise a plurality of tubes being spaced equally which carry the fluid heat exchange medium. In this aspect of the invention, the evaporator may further comprise an eliminator plate disposed at the first section for promoting uniform flow of refrigerant vapor through the integral subcooling means.

In a further aspect of the invention, there is provided an energy reclaim system comprising a compressor sub-system; a heat rejection sub-system and a cooling sub system, wherein the compressor sub-system comprises at least one compressor for drawing superheated refrigerant vapor for compression into high-pressure hot gas, a discharge line for conveying the high-pressure hot gas into a condenser within the heat rejection sub-system for condensing the high-pressure hot gas into refrigerant liquid while rejecting refrigeration heat, and a liquid line for conveying the refrigerant liquid to an integral subcooling means of an evaporator within the cooling sub system, the evaporator being adapted to expand the refrigerant liquid into a mixture of gas and liquid phases, a heat exchanger means being provided to cause the refrigerant liquid to boil at low pressure while extracting heat from a fluid heat exchange medium and the integral subcooling means to further superheat the refrigerant vapor for supply to a compressor of the energy reclaim system.

In this aspect of the invention, the heat rejection sub-system may further comprise a desuperheater having a heat exchanger means to provide a fluid heat exchange medium for absorbing heat from the compressed refrigerant to the fluid heat exchange medium.

In this aspect of the invention, the fluid heat exchange medium in the heat exchanger means may be passed to a chiller sub-system for absorbing heat dissipated from the chiller sub-system, and being delivered to the evaporator upon absorption of heat.

One skilled in the art will readily appreciate that the invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments described herein are not intended as limitations on the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

Fig. 1 is a diagram illustrating a side view of an evaporator for use within a cooling sub-system of an energy reclaim system;

Fig. 2 is a diagram illustrating a sectional view of an evaporator for use within a cooling sub-system of an energy reclaim system.; and

Fig. 3 is a schematic diagram illustrating an energy reclaim system comprising a compressor sub-system, a heat rejection sub-system and a cooling sub -system.

DETAILED DESCRIPTION OF THE INVENTION

Prior to discussing various embodiments of the invention, descriptions of some of the terms used herein are provided below for a better understanding of the invention.

As used herein, “energy reclamation” refers to any technique or method of minimizing the input of energy to an overall system by the exchange of energy from one sub-system of the overall system with another. As used herein, “refrigerant” refers to a substance used in a heat pump and refrigeration cycle that undergoes a phase change between gas and liquid. The refrigerant readily absorbs heat from the environment and can provide refrigeration or air conditioning when combined with other components such as compressors and evaporators. By way of examples but not by limitation, the refrigerant includes chlorofluorocarbons refrigerant, hydrochlorofluorocarbons refrigerant and hydrofluorocarbons refrigerant, and natural refrigerant. The refrigerant in gaseous and a liquid phase may be referred as refrigerant vapor and refrigerant liquid respectively.

As used herein,“fluid heat exchange medium” a liquid or a gas that transports heat from one component to another component in any process requiring heating or cooling or simply to maintain a constant temperature. A commonly used fluid heat exchange medium is water, which exhibits thermodynamic properties favourable to heat transfer.

The invention will now be described in greater detail, by way of example, with reference to the drawings. Fig. 1 and Fig. 2 depict an evaporator 1 for use within a cooling sub-system 2 of an energy reclaim system. In one preferred embodiment, the evaporator 1 is in the form of a water box having a substantially cylindrical hollow body 21 with both of its distal end each being secured by one dome-shaped cover 19 respectively. Preferably, the evaporator 1 is lifted from a ground surface by a plurality of base supports 20 that extend downwardly from the evaporator 1. In this exemplary embodiment, the evaporator 1 is adapted to receive a refrigerant liquid and expand the refrigerant into a gaseous and a liquid phase. By way of example, the refrigerant is refrigerant R134a. Preferably, the evaporator 1 comprises a first section and a second section for housing an integral subcooling means 4 and a heat exchanger means 3 therewithin, respectively.

The integral subcooling means 4 according to the present invention comprises an inlet tube 14 for receiving the refrigerant liquid from a condenser 9 and an outlet tube 15 for discharging the refrigerant liquid to an expansion valve 13. Preferably, the inlet tube 14 and the outlet tube 15 are suspended horizontally within the first section, in which the inlet tube 14 is disposed at a higher level than the outlet tube 15. Both the inlet tube 14 and the outlet tube 15 are supported by tube sheet 27. Preferably, the inlet tube 14 and the outlet tube 15 are oriented horizontally in order to minimize a vertical offset for eliminating oil logging within the integral subcooling means 4, particularly when the energy reclaim system operates at a part load condition. Furthermore, when the inlet tube 14 is placed higher than the outlet tube 15, such arrangement reduces operating pressure and thus reduces power consumption. The integral subcooling means 4 may have more than one inlet tube 14 and one outlet tube 15 in order to minimize pressure loss on the refrigerant liquid flowing through the tubes 14, 15.

The expansion valve 13 or an electronic expansion valve can be used interchangeable with a metering device and a throttling device. The expansion valve 13 expands the received refrigerant liquid into a gaseous and a liquid phase, which the mixture of refrigerant vapor and refrigerant liquid is passed into the water box, preferably through the second section.

The refrigerant liquid that enters the water box floods the second section as the second section is positioned beneath the first section, causing the heat exchanger means 3 to be at least partially submerged in the refrigerant liquid. Therefore, the evaporator 1 can also be known as flooded evaporator. The evaporator 1 further comprises a sight glass 22 to observe level of the refrigerant liquid within the second section and a float to control the level of refrigerant liquid refrigerant. Preferably, the heat exchanger means 3 carries a fluid heat exchange medium that is to be delivered to and received from another sub-system. The heat exchanger means 3 In one particular embodiment, the heat exchanger means 3 comprises a plurality of tubes being spaced equally which carry the fluid heat exchange medium. By way of example, the tubes may be arranged densely so that the fluid heat exchange medium dissipates heat to the refrigerant liquid that comes in contact with the tube. The fluid heat exchange medium to be used depends on the sub-system that connects to the heat exchanger means 3. By way of example but not by limitation, the heat exchanger means 3 may be connected to a chiller sub-system 11 and the fluid heat exchange medium may be in the form of water. Therefore, the heat exchanger means 3 causes the refrigerant liquid to boil at low pressure while extracting heat from the water to chill the water. Subsequently, the chilled water is delivered to the chiller sub-system 11 for distribution of chilled water to other facilities, such as a building.

The refrigerant liquid boiled by the heat exchanger means 3 is vaporised into refrigerant vapor. Both the refrigerant vapor resulted from boiling by the heat exchanger means 3 and the refrigerant vapor expanded by the expansion valve 13 that enters through the second section rises to the first section to be in contact with the integral subcooling means 4. Advantageously, the first section further comprises an eliminator plate 18 for promoting uniform flow of refrigerant vapor through the integral subcooling means 4. The integral subcooling means 4 further superheats the refrigerant vapor by absorbing heat from the refrigerant liquid for supply to a compressor 5 of the energy reclaim system. Upon heat removal, the refrigerant liquid within the integral subcooling means 4 becomes a subcooled refrigerant liquid with its enthalpy lowered followed by a corresponding gain in net enthalpy.

The superheated refrigerant vapor has its energy level elevated at an inlet condition of the compressor 5. The superheated refrigerant vapor picks up additional heat in the vapor compression cycle and elevates its energy level at the outlet condition of the compressor 5. In other word, the additional heat gained from the subcooled refrigerant liquid is transferred to high-pressure hot gas generated by compressor 5.

This process is accompanied with a reduction in the density of the superheated refrigerant vapor. Therefore, the capacity of the compressor 5 diminishes as a result of a reduction in the mass flow rate of the displaced refrigerant. Nevertheless, such set up does not compromise the ultimate cooling capacity of the energy reclaim system. The gain in the net enthalpy of the subcooled refrigerant liquid offsets the loss in the capacity of the compressor 5. A reduction in density of the superheated refrigerant vapor at the inlet condition of the compressor 5 brings about a reduction in the work done by the compressor 5 since the compressor power is directly proportional to the density of the refrigerant viper at the inlet condition of the compressor 5.

The evaporator 1 may further comprise a liquid line inlet connection 24 for connecting the integral subcooling means 4 to the condenser 9, a liquid line outlet connection 25 for connecting the integral subcooling means 4 to the expansion valve 9 and a distributor 28 disposed at the second section.

Preferably, the evaporator 1 is suitable to be used with refrigerant with high specific heat in its vapor phase. Synthetic lubrication oil is preferred as it is more stable at higher temperature.

Advantageously, oil separation between lubrication oil and refrigerant oil is improved with an increase in the discharge superheat. The nature and properties of the lubricant oil must be mixable with the refrigerant. Therefore, the oil carried from the compressor 5 or an oil separator is inevitable. However, the rate of oil loss is reduced with an increase in the discharge temperature with respect to the condensing temperature which is known as the discharge superheat. On the other hand, the performance of the condenser 9 and evaporator 1 is improved with less lubricant oil migrating into these parts of the system, which acts as an insulator to the heat transfer for the refrigerant. Furthermore, the life expectancy of the compressor 5 is extended with increased suction superheat, increased discharge superheat and reduced oil loss.

The energy reclaim system as depicted in Fig. 3 further comprises a compressor sub system 6 and a heat rejection sub-system 7. The compressor sub-system 6 comprises at least one compressor 5 coupled with a motor 26 for drawing superheated refrigerant vapor for compression into high-pressure hot gas. The compressor 5 may be a positive displacement refrigeration compressor which draws refrigerant vapor and compresses the refrigerant vapor into high-pressure hot gas with elevated boiling temperature.

The energy reclaim system further comprises a discharge line 8 for conveying the high-pressure hot gas into the condenser 9 within the heat rejection sub-system 7 for condensing the high-pressure hot gas into refrigerant liquid while rejecting refrigeration heat. The condenser 9 may be an air-cooled condenser or a water-cooled condenser. The air-cooled condenser consists of finned coils along with electric fan motors. The air-cooled condenser is used to reject refrigeration heat to the air passing through the coils while condensing desuperheated high-pressure hot gas into refrigerant liquid. The water-cooled condenser on the other hand consists of a shell-in tube heat exchanger used for rejecting refrigeration heat to the water circulating through the tubes while condensing desuperheated high-pressure hot gas into refrigerant liquid. The condenser 9 may be connected to a cooling water system 16. The cooling water system may comprise a cooling water pump for circulating cooling water between the condenser 9 and cooling tower system.

The refrigerant liquid is conveyed by a liquid line 23 to the integral subcooling means 4 of the evaporator 1 within the cooling sub-system 2. In one particular embodiment, the evaporator 1 is adapted to expand the refrigerant liquid into a mixture of gas and liquid phases. The heat exchanger means 3 within the evaporator 1 is provided to cause the refrigerant liquid to boil at low pressure while extracting heat from the fluid heat exchange medium. The integral subcooling means 4 further superheats the refrigerant vapor for supply to the compressor 5 of the energy reclaim system through means to facilitate 17 the drawing of the superheated gas refrigerant into the compressor 5.

Preferably, the fluid heat exchange medium in the heat exchanger means 3 is passed to a chiller sub-system 11 for absorbing heat dissipated from the chiller sub-system 11, and being delivered to the evaporator 1 upon absorption of heat. In one particular embodiment, the chiller sub-system 11 is a hydraulic pumping system having a chilled water circulation pump for circulating and distributing chilled water to airside units or other processes.

The heat rejection sub-system 7 may further comprise a desuperheater 12 having a heat exchanger means 10 to provide a fluid heat exchange medium for absorbing heat from the compressed refrigerant to the fluid heat exchange medium. In one particular embodiment, the heat exchanger means 10 may be a brazed plate heat exchanger or a shell-in-tube heat exchanger. The heat exchanger means 10 is used to recover refrigeration heat from desuperheating process, primarily for domestic hot water usage.

The present disclosure includes as contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the scope of the invention.

Claims

1. An evaporator (1) for use within a cooling sub-system (2) of an energy reclaim system, the evaporator (1) being adapted to receive a refrigerant liquid and expand the refrigerant into a gaseous and a liquid phase, a heat exchanger means (3) being provided to cause the refrigerant liquid to boil at low pressure while extracting heat from a fluid heat exchange medium and an integral subcooling means (4) to further superheat the refrigerant vapor for supply to a compressor (5) of the energy reclaim system.

2. The evaporator (1) according to claim 1, wherein the evaporator comprises a first section and a second section for housing the integral subcooling means (4) and the heat exchanger means (3) respectively.

3. The evaporator (1) according to claim 2, wherein the integral subcooling means (4) comprises an inlet tube (14) for receiving the refrigerant liquid from a condenser (9) and an outlet tube (15) for discharging the refrigerant liquid to an expansion valve (13).

4. The evaporator (1) according to claim 3, wherein the expansion valve (13) expands the received refrigerant liquid into a gaseous and a liquid phase.

5. The evaporator (1) according to claim 3, wherein the inlet tube (14) and the outlet tube (15) are disposed horizontally within the first section, in which the inlet tube (14) is disposed at a higher level than the outlet tube (15).

6. The evaporator (1) according to claim 3, wherein the heat exchanger means (3) comprises a plurality of tubes being spaced equally which carry the fluid heat exchange medium.

7. The evaporator (1) according to claim 2, further comprising an eliminator plate (18) disposed at the first section for promoting uniform flow of refrigerant vapor through the integral subcooling means (4).

8. An energy reclaim system comprising a compressor sub-system (6); a heat rejection sub-system (7) and a cooling sub-system (2), wherein the compressor sub-system (6) comprises at least one compressor (5) for drawing superheated refrigerant vapor for compression into high-pressure hot gas, a discharge line (8) for conveying the high- pressure hot gas into a condenser (9) within the heat rejection sub-system (7) for condensing the high-pressure hot gas into refrigerant liquid while rejecting refrigeration heat, and a liquid line (9) for conveying the refrigerant liquid to an integral subcooling means (4) of an evaporator (1) within the cooling sub-system (2), the evaporator (1) being adapted to expand the refrigerant liquid into a mixture of gas and liquid phases, a heat exchanger means (3) being provided to cause the refrigerant liquid to boil at low pressure while extracting heat from a fluid heat exchange medium and the integral subcooling means (4) to further superheat the refrigerant vapor for supply to a compressor (5) of the energy reclaim system.

9. The energy reclaim system according to claim 1, wherein the heat rejection sub system (7) further comprises a desuperheater (12) having a heat exchanger means (10) to provide a fluid heat exchange medium for absorbing heat from the compressed refrigerant to the fluid heat exchange medium.

10. The energy reclaim system according to claim 1, wherein the fluid heat exchange medium in the heat exchanger means (3) is passed to a chiller sub-system (11) for absorbing heat dissipated from the chiller sub-system (11), and being delivered to the evaporator (1) upon absorption of heat.