US20120297530A1

US20120297530A1 - Electrically insulated air-conducting water heater

Info

Publication number: US20120297530A1
Application number: US13/360,078
Authority: US
Inventors: Yen-Chieh Huang
Original assignee: National Tsing Hua University NTHU
Current assignee: National Tsing Hua University NTHU
Priority date: 2011-05-27
Filing date: 2012-01-27
Publication date: 2012-11-29
Also published as: TW201248094A; TWI429865B

Abstract

Electric shock to a user has been a major concern for a conventional electric water heater installed in or near a bathroom. An electrically insulated air-conducting water heater utilizes electrically insulating hot air to indirectly heat water to avoid electric hazard to a user of an electric water heater. The present invention comprises an air pump unit, a heating and temperature control unit, and an air venting unit having a plurality of tiny air nozzles immersed in a water pool. Ambient air is collected by the air pump unit, heated in the heating and temperature control unit, and injected into a water pool through the air venting unit as a form of zillions of small hot bubbles to heat the water. Apart from serving as an electrically safe water heater, the present invention also functions as a hot-bubble sauna machine, bathroom body dryer, and air conditioner.

Description

FIELD OF THE INVENTION

The present invention relates to a water heater, particularly to a water heater using electrically insulating air as a heat conducting medium to increase water temperature.

BACKGROUND OF THE INVENTION

In general, there are two types of water heaters, one burning natural gas and the other consuming electricity to raise the temperature of water. The latter is often adopted as a replacement for the former to avoid the danger of carbon-monoxide poisoning. However, a conventional electrical water heater employs an electric heating element or coil in direct contact with water through a heat conducting metallic material. In practice, only pure water is a good insulator. A user of an electric water heater could be constantly exposed to electric hazard when, for instance, taking a bath. The present invention overcomes this difficulty by adopting air, a much better electrically insulating medium, to conduct heat from an electric heating element to water. The present invention is not just an electrically safe water heater but also a hot-air sauna machine when injecting hot air into a bath tub. In a cold weather, the present invention can at the same time serve as an air conditioner or a comfortable body dryer in a bathroom.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to overcome the problem that the conventional electric water heater may cause electric shock to a user.
To achieve the abovementioned objective, the present invention discloses an electrically insulated air-conducting water heater, which applies a plurality of small hot air bubbles to heat water in a water pool. The present invention comprises an air pump unit, a heating and temperature control unit, and an air venting unit having a plurality of tiny air nozzles.
The air pump unit is an air pump that takes in ambient air and transports it into the heating and temperature control unit. The heating and temperature control unit raises the temperature of the air to a suitable level and generates hot air. The hot air propagates down an air conduit to an air venting unit placed in a water pool. Hot air is released into water through the air venting unit to heat the water.
The air venting unit has a plurality of tiny air nozzles, through which hot air is injected into water in the form of a great number of micro hot air bubbles. Since a micro air bubble has a smaller buoyant force compared with that of a large air bubble, a micro-bubble can be kept in water for a longer time to heat the water. Furthermore, the overall heating area of a great number of micro-bubbles can be significantly larger than that of a single large air bubble of the same volume Therefore, the heat stored in the air can be efficiently conducted to water. The following theory provides a concrete proof to the concept.
It is well known that heat transfer efficiency between two objects is proportional to the surface contact area between them. The following compares the surface area of a large air bubble with that of a number of small bubbles derived from the same air volume of the large bubble. Suppose that a large hot air bubble in water has a radius of r_b. Thus, the large hot air bubble has a surface area S_band a volume V_b, expressed by Equations (1,2), respectively:
S _b=4πr _b ² (1)
V _b=4πr _b ³/3 (2)
Suppose that the large hot air bubble is divided into N small air bubbles of the same size, and assume that each small air bubble has a radius of r_s. Thus, the total surface area of small air bubbles in contact with water S_sis given by Equation (3):
S _s =N4πr _s ² (3)
The total volume of the small hot bubbles V_scan be expressed by Equation (4):
V _s =N4πr _s ³/3 (4)
It is straightforward to obtain the ratio of the bubble's surface areas for the two cases by taking the ratio of Equations (1) and (3), given by:
S _s /S _b =N(r _s /r _b)² (5)
For a fair comparison, the air volume is kept constant or V_b=V_s. From Equations (2, 4), the following relationship holds for an equal air volume
N4πr _s ³/3=4πr _b ³/3 (6)
or
r _s /r _b=(1/N)^1/3 (7)
By substituting Equation (7) into (5), the area ratio S_s/S_bbecomes:
S _s /S _b =N ^1/3 (8)
Equation (8) clearly shows that a large amount of small air bubbles can have a much larger heat-transfer contact area than does a single large air bubble of the same air volume. Suppose that a plurality of tiny air nozzles divide a large hot air bubble into one million small hot air bubbles. According to Equation (8), the surface area of all the small hot air bubbles is 100 (=(1,000,000)^1/3) times greater than that of the large hot air bubble. Thus, the heating efficiency of those small hot air bubbles is 100 times that of the single large hot air bubble. Normally, it is not difficult to fabricate tiny air nozzles on an air venting unit. For example, laser micro-machining is a convenient technique to drill micro-air nozzles on materials.
As mentioned above, a smaller hot bubble has smaller buoyant force and can stay in water over a longer time. According to the Archimedean principle, a body immersed in a fluid gets a buoyant force F_Bequal to the weight of the fluid it displaces. In other words, a bubble experiences a buoyant force equal to the weight of the water having the same volume as the bubble:
F _B =ρVg (9)
where V is the volume of a bubble, p is the density of a fluid, and g is the gravitational acceleration. It is evident from Equation (9) that the buoyant force F_Band thus the upward acceleration of the bubble in water are proportional to its own volume. In other words, a smaller hot bubble can stay in water longer than a larger one. This increased heating time allows the smaller hot air bubbles to transfer more heat to water.
Thus, the disclosure of using a large amount of hot micro-bubbles to heat water is a key technical advancement of the present invention. The small bubble size not only increases the heat transfer area between air and water but also increases the heating time of air to water. This technical advancement effectively increases the heat transfer efficiency from hot air to water.
The air venting unit further comprises an air-storage volume and a thermal conductive structure. The air venting unit is immersed in water in a water pool or a bath tub. The thermal conductive structure is made of heat conducting materials with two planar sides, one exposed to the air-storage volume and the other exposed to water in the water pool. The hot air propagates down the air venting unit through an air conduit. The heat energy stored in the hot air can be quickly transferred to water via the thermal conductive structure in contact with the air-storage volume. The tiny air nozzles of the air venting unit divide the hot air into small hot bubbles. The residual heat energy stored in the hot air is carried to the small hot air bubbles and released to water.
In summary, ambient air is taken into an air pump unit and heated by the heating and temperature control unit to form hot air. The hot air is sent into an air venting unit through an air conduit. When the hot air is transported into an air storage volume in contact with a thermal conductive structure in the air venting unit, the hot air quickly transfers part of its heat energy to the thermal conductive structure to heat up the temperature of the water in contact with the other side of the thermal conductive structure. The hot air in the air-storage volume is then released to water through a plurality of tiny air nozzles, which generate a large number of air bubbles to continuously transfer heat to water, massage a user in a bath tub, or warn up the temperature of a cold bathroom.
According to the aforementioned concepts, the present invention employs electrically insulating hot air as a heating medium for a water heater. Electric energy is first transferred to heat energy stored in air, which is then transferred to water through a thermal conductive structure, or a large number of hot air bubbles in water, or both. This water heating process ensures electric insulation between the electricity and a user in water. The high speed air bubbles ejected from the tiny air nozzles in the air venting unit can at the same time generate ultrasound to massage or clean a user in the water pool, dry the body of a person or a pet animal, and warm up a cold bathroom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing the structure of electrically insulated air-conducting water heater according to the present invention;

FIG. 2 is a diagram schematically showing the structure of an electrically insulated air-conducting water heater according to a first embodiment of the present invention;

FIG. 3 is a diagram schematically showing a detailed air venting unit of an electrically insulated air-conducting water heater according to the first embodiment of the present invention; and

FIG. 4 is a diagram schematically showing the structure of an electrically insulated air-conducting water heater according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The technical contents of the present invention are described in details with reference to the drawings above.
Refer to FIG. 1, a diagram schematically showing the structure of an electrically insulated air-conducting water heater according to the present invention. The water heater of the present invention uses a plurality of small hot bubbles 4 to heat water 3 in a water pool 5, comprising an air pump unit 10, a heating and temperature control unit 20, and an air venting unit 30. The air pump unit 10 takes in the ambient air 1 via an air inlet 11, and then sends the ambient air 1 to the heating and temperature control unit 20 via an air channel 23. The heating and temperature control unit 20 heats the ambient air 1 to form hot air 2. The hot air 2 is sent to the air venting unit 30 via an air conduit 31. A plurality of tiny air nozzles 32 of the air venting unit 30 divides the hot air 2 into a plurality of small hot bubbles 4. The small hot bubbles 4 are released to the water 3 to heat the water 3.
Refer to FIG. 2 a diagram schematically showing the structure of an electrically insulated air-conducting water heater according to a first embodiment of the present invention. The air pump unit 10 has an air inlet 11 to take in the ambient air 1 and then pump the ambient air 1 to the heating and temperature control unit 20. In the first embodiment, a filter 111 is arranged inside the air inlet 11 to prevent foreign objects from entering the air pump unit 10. The heating and temperature control unit 20, following the air pump unit 10 through an air channel 23, heats the ambient air 1 sent down by the air pump unit 10. The hot air 2 propagates down the air conduit 31 to reach the air venting unit 30. The air venting unit 30 is immersed in the water pool 5 and has a plurality of tiny air nozzles 32 on the surface enclosing an air-storage volume 33. The hot air 2 transferred to the air-storage volume 33 is then divided into a plurality of small hot bubbles 4 by a plurality of tiny air nozzles 32 of the air venting unit 30. Then, the hot air 2 is released to the water 3 in the form of small hot bubbles 4. In the first embodiment, the tiny air nozzles 32 are distributed on a surface of the air venting unit 30. The diameter of the tiny air nozzles 32 is varied according to the desired heating rate to water. For example, tiny air nozzles 32 having smaller diameters can generate smaller hot bubbles 4 and increase the total number of the bubbles 4 in water. As previously proved, the small bubble can favorably increase the heat transfer area between and contact time of the hot air and water. The diameters of the tiny air nozzles 32 are preferably between 1 and 1000 μm. Alternatively, the tiny air nozzles 32 can be distributed on selective sides or certain area of the air venting unit 30. For example, under certain situation, a user 6 immersed in a bath tub might want to avoid direct contact with the hot-air nozzles.
The air venting unit 30 may further comprise a thermal conductive structure 37 having two opposite surfaces. The thermal conductive structure 37 is made of partially or fully heat conducting materials with two surfaces. One surface is exposed to the air-storage volume 33 to extract heat from the hot air, and the other is exposed to the water 3 in the water pool 5 to release heat to the water. In the first embodiment, the thermal conductive structure 37 is arranged at one side of the air venting unit 30, facing down the bottom of the water pool 5 to avoid a direct contact with a user 6. The thermal conductive structure 37 can be a high thermal-conductivity material such as a metal plate with or without a honeycomb structure, or simply some plastic or rubber with good heat conductivity.
Refer to FIG. 3, a diagram schematically showing a detailed air venting unit of an electrically insulated air-conducting water heater according to the first embodiment of the present invention. In the first embodiment, an air-impermeable plastic or rubber film 36 partitions the air-storage volume 33 into a upper heat transfer compartment 331 and a lower heat transfer compartment 332. The lower heat transfer compartment 332 having one side joint with the thermal conductive structure 37. The hot air 2 propagates down the air conduit 31, enters the lower heat transfer compartment 332 first, and then enters the upper heat transfer compartment 331. As a result, the heat energy stored in the hot air 2 is first transferred to the thermal conductive structure 37 and then released to water through the tiny air nozzles 32. Specifically, when passing through the lower heat transfer compartment 332, the hot air 2 contacts the thermal conductive structure 37. The thermal conductive structure 37 comprises a sheet or a plurality of thermal conductive elements 371 and a plurality of air nozzles 372. The air nozzles 372 are interleaved with or fabricated on the thermal conductive element 371. When the hot air 2 passes the lower heat transfer compartment 332, the heat energy stored in the hot air 2 is transferred to the water 3 through the thermal conductive element 371 and some hot air 2 is released to the water 3 in the form of small hot bubbles 4 via the air nozzles 372. The thermal conductive element 371 may be made of a material such as plastic, rubber, or metal having a good thermal conductivity. The remaining hot air 2 continues to propagate into the upper heat transfer compartment 331 and enter the water 3 in the form of small hot bubbles 4 via the tiny air nozzles 32 on the top surface of the upper heat transfer compartment 331. The hot bubbles 4 exiting the tiny air nozzles 32 provide further heating to the water 3. The user 6 can also enjoy a sauna bath from those bubbles, getting herself or himself cleaned, massaged, and relaxed. Further, the hot air 2 going out from the water 3 can be used to warm up a bathroom in a cold weather. The air-impermeable plastic film 36 separate the air-storage volume 33 into the upper heat transfer compartment 331 and lower heat transfer compartment 332. Since the heat is first released to the lower heat transfer compartment 332, this embodiment of the present invention keeps a high temperature zone facing the bottom of the water pool but not facing the user 6. To a user's comfort, a user can certainly adjust the heat transfer rate by varying the pumping and heating speed from the air pump unit 10 and the heating and temperature control unit 20, respectively.
The air venting unit 30 may further have at least one sucking disk 35 on the surface facing the bottom of the water pool 5. In the first embodiment, the air venting unit 30 is fixed to the bottom of the water pool 5 or commonly a bathtub by a plurality of sucking disks 35. The sucking disks 35, with some finite height, can provide a gap space between the thermal conductive structure 37 and the bottom of the water pool 5, in which the water 3 can contact the thermal conductive structure 37 to absorb the heat energy from the thermal conductive structure 37. In the first embodiment, a plurality of protrusions 34 is arranged on the upper surface of the air venting unit 30. The protrusions 34 on one hand prevent a user from blocking the air nozzles 32 when lying on the air venting unit 30, and on the other hand provide some pressure points to a user when a user lies in the water pool 5 to enjoy sauna massage.
Refer to FIG. 4, a diagram schematically showing the structure of an electrically insulated air-conducting water heater according to a second embodiment of the present invention. In the second embodiment, the heating and temperature control unit 20 includes an electric heater 21 and a temperature controller 22. The electric heater 21 heats the ambient air 1 entering the heating and temperature control unit 20 to form the hot air 2. The temperature controller 22 controls the heating intensity of the electric heater 21 according to a user pre-set temperature for the hot air. In the second embodiment, the air conduit 31 further has at least one air outlet 311 a, 311 b and 311 c. The hot air 2 is directly blown into the open space from the air outlets 311 a and 311 b without going through the water in the water pool 5. The user 6 may use the hot air 2 from the air outlets 311 a and 311 b to dry hairs, hands, or any other part of the user's body. Therefore, the present invention also functions as a hair dryer and a hand dryer. In a cold environment, additional air outlet 311 c can be extended from the air conduit 31 to serve as a warm air source of an air conditioner. Further, a plurality of air directing fins 312 may be arranged in the air outlet 311 c to adjust and control the flow direction of the hot air 2. It should be pointed out that the layout of the air conduits and outlets shown in FIG. 4 is not a unique one but only to exemplify the concept of the present invention. The present invention may adopt a different arrangement for the air conduits and outlets at different locations, angles, and heights to meet the functional purposes of a hair dryer, hand dryer, body dryer, or air conditioner. For example, a flexible bellow-type air conduit with an outlet can be provided to a user for convenience of usage. Furthermore, a control valve 313 may be used to switch the hot air 2 to blow out from a single air outlet or from multiple air outlets simultaneously. The functions of the present invention are not limited to serving a human user but can be extended to serving a pet animal.
In conclusion, the electrically insulated air-conducting water heater of the present invention adopts non-conducting air as a heat-transfer medium to heat water, so as to avoid potential electric hazard to a hot-water user. The non-conducting air is collected by an air pump, heated electrically in the heating and temperature control unit of the present invention, and injected into water directly as a form of bubbles to heat water. To effectively transfer the stored thermal energy in the hot air to water, injecting micro-bubbles into water from micron-size air nozzles is disclosed as a major advancement and key embodiment of the present invention. A second embodiment of the present invention is to firstly transfer part of the thermal energy of the hot air to a thermally conductive material in contact with water and secondly inject the hot air bubbles into water for further water heating. A user of the present invention can adjust the temperature of the air through the heating and temperature control unit of the present invention according to the desired water-heating rate, the desired bathroom temperature, or personal joy and comfort from a hot-bubble sauna. The present invention can function simultaneously as an electrically safe water heater, a hot-bubble sauna machine, a hand dryer, a hair dryer, a body dryer, and an air conditioner to a human user or a pet animal.
The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention. For example, the generation of the hot air does not require an installation of the air pump unit in front of the heating and temperature control unit. A system reversing the sequence of the installation is still well within the scope of the present invention. Also, the diameters of the air nozzles are not necessarily uniform for all nozzles. The present invention can adopt different size nozzles at different locations on the air venting unit to optimize the heating rate to water and the comfort to a user.

Claims

1. An electrically insulated air-conducting water heater, which uses a plurality of hot air bubbles to heat water in a water pool, comprising

an air pump unit including an air inlet to collect ambient air and then press forward the ambient air;.

a heating and temperature control unit connecting with the air pump unit to heat the ambient air pressed down by the air pump unit to form hot air; and

an air venting unit including a plurality of tiny air nozzles, immersed in the water pool, connecting with the heating and temperature control unit to receive the hot air via an air conduit, and releasing the hot air via the tiny air nozzles.

2. The electrically insulated air-conducting water heater according to claim 1, wherein the air venting unit includes an air-storage volume and a thermal conductive structure, and wherein the thermal conductive structure includes two opposite surfaces, one in contact with water and the other in contact with hot air.

3. The electrically insulated air-conducting water heater according to claim 2, wherein the thermal conductive structure is arranged on one side of the air venting unit, facing down the bottom of a water pool.

4. The electrically insulated air-conducting water heater according to claim 2, wherein the air venting unit includes at least one sucking disk on the surface facing the bottom of the water pool.

5. The electrically insulated air-conducting water heater according to claim 2, wherein an air-impermeable plastic film partitions the air-storage volume into an upper heat transfer compartment and a lower heat transfer compartment, and wherein one side of the lower heat transfer compartment joins with the thermal conductive structure.

6. The electrically insulated air-conducting water heater according to claim 1, wherein the air venting unit includes a plurality of protrusions arranged on the upper surface thereof.

7. The electrically insulated air-conducting water heater according to claim 2, wherein the thermal conductive structure is made of a material selected from a group consisting of metal, plastic, and rubber.

8. The electrically insulated air-conducting water heater according to claim 1, wherein the tiny air nozzles have aperture diameters between 1 and 1000 μm.

9. The electrically insulated air-conducting water heater according to claim 1, wherein the air inlet includes a filter arranged inside.

10. The electrically insulated air-conducting water heater according to claim 1, wherein the air conduit further includes at least one air outlet directly blowing the hot air to the space outside the water pool.

11. The electrically insulated air-conducting water heater according to claim 10, wherein a plurality of air directing fins arranged in the air outlet to adjust and control the flow direction of the hot air.

12. The electrically insulated air-conducting water heater according to claim 1, wherein the heating and temperature control unit includes an electric heater to heat the air.

13. The electrically insulated air-conducting water heater according to claim 1, wherein the heating and temperature control unit includes a temperature controller for a user to set the temperature of the air.