FIELD OF THE INVENTION

The invention relates to the field of heat exchange, particularly an apparatus for heat transfer between fluids and a fluid treating system involving the apparatus. More particularly, the apparatus includes two separate conduit assemblies, each for a first fluid and a second fluid, and a heat transfer medium for performing heat transfer between the first fluid and the second fluid.

BACKGROUND OF THE INVENTION

Water heaters are one of the common home appliances. Conventional water heaters use electrical energy to heat water directly. Heat pump water heaters, on the other hand, use electrical energy to move heat from a source, such as air or liquids, to the water instead of heating the water directly. In integrated air conditioning and water heating systems, waste heat produced by the air conditioning circuit will be transferred to the water via a heat exchanger connecting the air conditioning circuit to the water heating circuit.

There are several types of heat exchanger for heat pump water heaters. In heat exchangers that involve direct heating, water fills the heat exchanger and a copper tube through which refrigerant flows is immersed in the water. The heat in the refrigerant will be transferred to the water directly. Nevertheless, a few drawbacks for this type of heat exchanger have been reported. One of the drawbacks is fouling of the copper tube. De-scaling of the copper tube is required when fouling occurs, but it is difficult to be carried out as the tube is sealed within the heat exchanger. Another drawback reported is the mixing of the refrigerant and water when the copper tube leaks which j eopardizes people who use the heated water that is contaminated with refrigerant.

Another type of heat exchanger for heat pump water heaters includes a water storage tank with copper tube, through which the refrigerant flows, wrapped around it to transfer the heat in the refrigerant to the water in the storage tank. This type of heat exchanger prevents intermixing of refrigerant and water when the copper tube leaks. However, the heat transfer process is relatively slower such that a longer time is needed to heat the water to a certain temperature.

Double wall heat exchangers have been introduced to ensure refrigerant and water do not mix in the event of tube leakage. In double wall heat exchangers, refrigerant and water are directed to flow through separate plates that are stacked upon one another with an air gap in between two plates. The air gap makes any internal leaks visible by allowing the leaked liquid to seep out through the air gap to the atmosphere. Nevertheless, since air is a heat insulator, the air gap hinders heat transfer between the plates. Hence, double wall heat exchangers generally take longer time to heat the water to a certain temperature as compared to the direct heat exchanger.

Therefore, there exist needs for a heat exchanger for heat pump water heaters which prevents refrigerant and water from mixing in case of any internal leakage and allows water to be heated to a certain temperature within a relatively shorter period.

SUMMARY OF THE INVENTION

The primary object of the invention is to provide an apparatus for transferring heat between a first fluid and a second fluid, such that the two fluids flow through individual conduit assemblies and do not mix when internal leak happens.

Another object of the invention is to provide an apparatus for transferring heat between a first fluid and a second fluid comprising a heat transfer medium for facilitating the heat transfer between the fluids. Preferably, the heat transfer medium has a low specific heat capacity. More preferably, the heat transfer medium is anti -corrosive.

Further another obj ect of the invention is to provide an apparatus for transferring heat between refrigerant and a liquid whereby the refrigerant releases or absorbs heat at the apparatus while the liquid is heated or cooled at the apparatus. Still another object of the invention is to provide an apparatus for transferring heat between refrigerant and water, particularly refrigerant of an air conditioning circuit and water of a water heating circuit.

Yet another object of the invention is to provide a fluid treating system comprising the aforementioned apparatus, a first circuit in which the first fluid circulates and a second circuit in which the second fluid circulates. Preferably, one or multiple first circuits can be connected to one or more apparatus for heat transfer with one or multiple second circuits.

At least one of the preceding objects is met, in whole or in part, by the present invention, in which the embodiment of the present invention describes an apparatus for transferring heat between a first fluid and a second fluid, comprising a receptacle; a first conduit assembly contained within the receptacle through which the first fluid flows; a second conduit assembly contained within the receptacle through which the second fluid flows; and a heat transfer medium contained within the receptacle and being in contact with the first conduit assembly and the second conduit assembly to perform heat transfer between the first fluid and the second fluid; wherein the heat transfer medium has a specific heat capacity of 0.1 to 5.0 kJ/kgK.

In a more preferred embodiment of the invention, the heat transfer medium has a specific heat capacity of 0.5 to 2.0 kJ/kgK.

In a preferred embodiment of the invention, the heat transfer medium is anti -corrosive.

In a preferred embodiment of the invention, the heat transfer medium is mineral oil.

In a preferred embodiment of the invention, the apparatus further comprises a layer of heat insulating material deposited on an outer surface of the receptacle.

In a preferred embodiment of the invention, the first fluid is a refrigerant that is in a form of liquid or vapor for absorbing or releasing heat at the apparatus. In a preferred embodiment of the invention, the second fluid is a liquid being heated or cooled at the apparatus.

In a preferred embodiment of the invention, the first conduit assembly is involved in a refrigeration circuit in which the first fluid circulates. Preferably, the refrigeration circuit is an air conditioning circuit.

In a preferred embodiment of the invention, the second conduit assembly is involved in a liquid treating circuit in which the second fluid circulates. Preferably, the liquid treating circuit is a water heating circuit.

The present invention also describes a fluid treating system, comprising a first circuit in which a first fluid circulates; a second circuit in which a second fluid circulates; and an apparatus for transferring heat between the first fluid and the second fluid which comprises a receptacle; a first conduit assembly contained within the receptacle and being involved in the first circuit in which the first fluid circulates; a second conduit assembly contained within the receptacle and being involved in the second circuit in which the second fluid circulates; and a heat transfer medium contained within the receptacle and being in contact with the first conduit assembly and the second conduit assembly to perform heat transfer between the first fluid and the second fluid; wherein the heat transfer medium has a specific heat capacity of 0.1 to 5.0 kJ/kgK.

In a more preferred embodiment of the invention, the heat transfer medium has a specific heat capacity of 0.5 to 2.0 kJ/kgK.

In a preferred embodiment of the invention, the heat transfer medium is anti-corrosive.

In a preferred embodiment of the invention, the heat transfer medium is mineral oil.

In a preferred embodiment of the invention, the first circuit is a refrigeration circuit whereby the first fluid being refrigerant is applied to absorb or release heat at the apparatus. Preferably, the refrigeration circuit is an air conditioning circuit. In a preferred embodiment of the invention, the second circuit is a liquid treating circuit whereby the second fluid being liquid is heated or cooled at the apparatus. Preferably, the liquid treating circuit is a water heating circuit.

In a preferred embodiment of the invention, the second circuit comprises a fluid storage tank for collecting treated fluid defined by the second fluid from the second conduit assembly upon being subjected to heat transfer at the apparatus. Preferably, the fluid storage tank is a water storage tank.

In a preferred embodiment of the invention, the treated fluid is directed out from the fluid storage tank for consumption or usage.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings 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 will be readily understood and appreciated.

Figure 1 is a schematic drawing of an apparatus for transferring heat between a first fluid and a second fluid embodying the present invention.

Figure 2 is a schematic diagram of a fluid treating system embodying the present invention.

Figure 3 illustrates the fluid treating systems described in Example 1 , whereby (a) shows a single pass water heating system and (b) shows a recirculating water heating system.

Figure 4 is a graph showing the time needed to prepare 10 litre of water at 60 °C using the fluid treating system of the invention. DETAILED DESCRIPTION OF THE INVENTION

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

The present invention describes an apparatus (100) for transferring heat between two fluids. Figure 1 illustrates a preferred embodiment of the apparatus (100). The apparatus (100) comprises a receptacle (101) with a hollow body. Contained within the receptacle (101) are a first conduit assembly (102) through which a first fluid flows and a second conduit assembly

(103) through which a second fluid flows. Preferably, the conduits in the conduit assemblies are made of heat conductive material. The first conduit assembly (102) and the second conduit assembly (103) are preferred to be intertwined or stacked upon each other. Besides, the flow of first fluid and second fluid in the conduits may be in the same direction (parallel flow) or opposite directions (counter flow). In addition to the conduit assemblies, a heat transfer medium (104) is contained within the receptacle (101) to facilitate heat transfer between the first fluid and the second fluid. Particularly, the heat transfer medium (104) fills the space within the receptacle (101) and is in contact with the first conduit assembly (102) and the second conduit assembly (103). The heat from one of the first fluid or the second fluid which has a higher temperature will be released to the heat transfer medium (104), which in turn releases the heat to the other of the first fluid or the second fluid which has a lower temperature. In a further embodiment of the invention, the apparatus (100) may comprise a layer of heat insulating material (not shown in Figure 1) deposited on an outer surface of the receptacle (101) to prevent heat loss to the surroundings.

In a preferred embodiment of the invention, the heat transfer medium (104) employed in the apparatus (100) has a specific heat capacity of 0.1 to 5.0 kJ/kgK, or more preferably 0.5 to 2.0 kJ/kgK. The relatively low specific heat capacity of the heat transfer medium (104) allows it to absorb or release heat quickly. Therefore, the heat transfer between the heat transfer medium

(104) and the first fluid, and the heat transfer medium (104) and the second fluid, and the overall heat transfer between the first fluid and the second fluid is sped up. Preferably, the heat transfer medium (104) is anti-corrosive so as to reduce if not prevent corrosion of the conduits that will subsequently cause leakage of the fluids. Any liquid or solid can be used as the heat transfer medium (104) in the apparatus (100) disclosed herein provided that it has a specific heat capacity in the range of 0.1 to 5.0 kJ/kgK and is anti-corrosive. Nevertheless, it is preferred that mineral oil is used as the heat transfer medium (104). With the application of mineral oil as the heat transfer medium (104), there will be reduction or elimination of air resistance against the heat transfer between first conduit assembly (102) and second conduit assembly (103) and thus improves the overall heat transfer efficiency.

The first fluid and the second fluid can be in liquid or gaseous state. The first fluid may be similar or different to the second fluid. In a preferred embodiment of the invention, the first fluid is a refrigerant that is in a form of liquid or vapor for absorbing or releasing heat at the apparatus (100) while the second fluid is a liquid being heated or cooled at the apparatus (100), or vice versa. Particularly, the refrigerant is in form of vapor if it is used to release heat to the liquid in the apparatus (100) and it is in form of liquid if it is used to absorb heat from the liquid in the apparatus (100). In another embodiment of the invention, both the first fluid and the second fluid are refrigerant that is in a form of either liquid or vapor for absorbing or releasing heat at the apparatus (100). In still another embodiment of the invention, both the first fluid and the second fluid are liquid that is to be heated or cooled at the apparatus (100).

The conduit assemblies (102, 103) of the invention may involve in a refrigeration circuit, a liquid treating circuit, or both. Pursuant to a preferred embodiment of the invention, the first conduit assembly (102) is involved in a refrigeration circuit in which the first fluid circulates. Preferably, the refrigeration circuit is an air conditioning circuit. Meanwhile, the second conduit assembly (103) is involved in a liquid treating circuit in which the second fluid circulates. Preferably, the liquid treating circuit is a water heating circuit. In another preferred embodiment of the invention, the first conduit assembly (102) is involved in a liquid treating circuit in which the first fluid circulates while the second conduit assembly (103) is involved in a refrigeration circuit in which the second fluid circulates.

The present invention also describes a fluid treating system (200). In a preferred embodiment of the invention, which is depicted in Figure 2, the system comprises a first circuit (201) in which a first fluid circulates, a second circuit (202) in which a second fluid circulates, and an apparatus (100) for transferring heat between fluids as described in preceding description. In another embodiment of the invention, the system (200) may comprise one or multiple first circuits (201) which can work within one or multiple apparatuses (100) for heat transfer with one or multiple second circuits (202). The first circuit (201) and/or the second circuit (202) may comprise one or more heat exchangers (203). As shown in Figure 2, two heat exchangers (203) are involved in the first circuit (201), one being evaporator while the other one being condenser. Treated fluid, defined by the second fluid from the second conduit assembly (103) upon being subjected to heat transfer at the apparatus (100), can be directed out from the apparatus (100) for consumption or usage. Activities involving consumption or usage of the treated fluid includes, but not limited to, washing, laundry, drinking, cooking, etc. The second circuit (202) may further comprise a fluid storage tank (205) for collecting treated fluid. The treated fluid can be directed out from the fluid storage tank (205) for consumption or usage. The treated fluid in the fluid storage tank (205) may also be redirected to the apparatus (100) for additional round(s) of heat transfer at the apparatus (100) in order to reach a predetermined temperature. Preferably, the fluid storage tank (205) stores treated fluid at a temperature not lower than 60 °C to prevent growth of microorganisms therein.

In accordance to the preferred embodiment, the apparatus (100) contains a heat transfer medium (104) which has a specific heat capacity of 0.1 to 5.0 kJ/kgK, or more preferably 0.5 to 2.0 kJ/kgK. Preferably, the heat transfer medium (104) possesses anti-corrosive property. The heat transfer medium (104) can be any liquid or solid as long as its specific heat capacity falls in the range of 0.1 to 5.0 kJ/kgK and it is anti-corrosive. Preferably, mineral oil is used as heat transfer medium (104) in the apparatus (100).

In a preferred embodiment of the invention, the first circuit (201) is a refrigeration circuit whereby the first fluid being refrigerant is applied to absorb or release heat at the apparatus (100). The first circuit (201) may further comprise a compressor (204) and at least one heat exchanger (203) playing the role of evaporator or condenser. Preferably, the refrigeration circuit is an air conditioning circuit. In case where refrigerant is expected to release heat in the apparatus (100), the first circuit (201) comprises a compressor (204) and at a heat exchanger (203) as evaporator to absorb heat from the ambient environment and provide cooled air. In case where refrigerant is expected to absorb heat in the apparatus (100), the first circuit (201) comprises a compressor (204) and at least a heat exchanger (203) as condenser to release heat to the ambient environment and provide heated air.

In a preferred embodiment of the invention, the second circuit (202) is a liquid treating circuit whereby the second fluid being liquid is heated or cooled at the apparatus (100). The second circuit (202) may further comprise a pump (206) for controlling inflow of the liquid into the apparatus (100). Preferably, the liquid treating circuit is a water heating circuit whereby water is directed into the apparatus (100) to absorb heat released from the first fluid, particularly refrigerant in vapor form. The fluid storage tank (205) is preferred to be a water storage tank in which heated water can be discharged therefrom for consumption or usage. For instance, the heated water stored in the water storage tank (205) can be used for showering, drinking, cooking, etc. Preferably, the heated water stored in the water storage tank (205) has a temperature not lower than 60 °C so as to prevent proliferation of harmful microorganisms such as Legionella bacteria inside the water storage tank.

EXAMPLE

An example is provided below to illustrate different aspects and embodiments of the invention. The example is not intended in any way to limit the disclosed invention, which is limited only by the claims.

In an experimental test, a fluid treating system (200) of the invention is used to heat 10 litre of water to 60 °C. Particularly, a water heating system integrated with an air conditioning system is used. In the test, water is directed into the apparatus (100) for heat transfer either once or multiple times. Figure 3 illustrates a single pass water heating system and a recirculating water heating system. In single pass water heating system, cold water from external water supply enters to the apparatus (100) for one-time heat transfer process, whereby hot water is generated and transferred out to be used directly or to be stored in a water tank. On the other hand, a recirculating water heating system requires a water storage tank (205) with aid of pump (206) for circulating water from the water storage tank (205) into the apparatus (100) for continuous heating process. External water supply is provided to the water storage tank (205) for continuous water supply. The time taken for 10 L of water to reach 60 °C in single pass water heating system and recirculating water heating system are recorded respectively. Figure 4 and Table 1 shows the results of the experimental test.

Referring to Figure 4 and Table 1, it was shown that single pass system was able to provide higher temperature and shorter heating time, i.e. 64.2 °C in 38.5 minutes, when compared to the recirculation systems. It is interesting to note that for recirculation system, the first half of the heating cycle was relatively quick, as shown for the recirculation cycle for the 2.3 L/min, it only takes 28.3 minutes for water to be heated up to 55 °C from a starting temperature of approximately 30 °C. However, it takes about the same amount of time to heat up 10 L of water from 55 °C to 60 °C due to the temperature pinch effect.