[DESCRIPTION]

[Invention Title]

HEAT PUMP

[Technical Field]

The present invention relates to a heat pump.

[Background Art]

A heat pump is an air conditioning device capable of reversing the flow of

refrigerant in the refrigeration cycle of a packaged air conditioner to selectively provide

cooling and heating, and is currently widely used because of its usefulness regardless of

season and because of its low load with respect to environmental pollution.

Fig. 1 is a diagram illustrating a conventional heat pump system, composed of a

compressor 1 which compresses the refrigerant, an indoor heat exchanger 2 at which the

high-temperature high-pressure refrigerant compressed at the compressor 1 is condensed

into a liquid state, an indoor fan 3, an expansion valve 4 which expands the liquid

refrigerant condensed at the indoor heat exchanger 2 into a 2-phase state of liquid and

vapor, an outdoor heat exchanger 5 at which the refrigerant, changed into a 2-phase state

due to the lowering of pressure and temperature while passing through the expansion

valve 4, is evaporated into a vapor state, an outdoor fan 6, and a 4-way valve 7 which

alters the flow path of the refrigerant according to the selection of a cooling or heating

mode. In Fig. 1, the arrows represent the direction of flow of the refrigerant.

The heating operation proceeds as follows for a heat pump comprised as above.

First, when power is supplied to the heat pump, the refrigerant is drawn into the

compressor 1. The high-temperature high-pressure compressed refrigerant is drawn into

the indoor heat exchanger 2 to be changed into a 2-phase state of liquid and vapor, and

with continued heat exchange, the refrigerant is changed into a liquid state at the outlet

side of the indoor heat exchanger 2. Here, indoor air is drawn by the rotating of the indoor

fan 3 into the indoor heat exchanger 2 and undergoes heat exchange with the

high-temperature high-pressure refrigerant, after which it is drawn into the indoor space

for heating the indoor space. The liquid refrigerant condensed at the indoor heat

exchanger 2, while passing the expansion valve 4, is drastically lowered in pressure and

temperature and is changed into a 2-phase state of liquid and vapor, to be drawn into the

outdoor heat exchanger 5. The 2-phase state refrigerant drawn into the outdoor heat

exchanger 5 undergoes heat exchange with outdoor air to be evaporated into a vapor state,

and is drawn again into the compressor 1 to repeat the cycle.

Here, as the heat exchange action at the outdoor heat exchanger 5 is of absorbing

heat from the drawn-in outdoor air, a temperature difference is created between the inside

and outside of the outdoor heat exchanger 5. For example, when the temperature of the

outdoor air is 7 ⁰ C, a heat pump cycle is formed with a temperature of about 1 to 2 ⁰ C in

the outdoor heat exchanger 5, and if the outdoor air temperature is lowered even further,

the temperature of the outdoor heat exchanger 5 is lowered below 0 ⁰ C.

When the temperature difference between the inside and outside of the outdoor

heat exchanger 5 exceeds a certain level (generally 5 to 7 ⁰ C), frost is created on the outer

wall of the outdoor heat exchanger 5. Such a frosting phenomenon generally occurs after

30 minutes' operation of the heat pump. Such a frost layer not only acts as thermal

resistance which impedes heat transfer between the air and the refrigerant, but also blocks

the flow path of outdoor air passing through the outdoor heat exchanger 5 to increase the

system resistance of the air, which reduces the amount of airflow drawn into the outdoor

heat exchanger 5 and decreases the coefficient of heat transfer of the outdoor heat

exchanger 5, whereby the amount of heat transfer at the outdoor heat exchanger 5 is

reduced.

To prevent such frosting, a conventional heat pump used a defrosting operation,

in which the refrigerant was flowed in a direction opposite the flow for the heating

operation. However, when the flow of the refrigerant is altered from that of the heating

mode to that of the defrosting mode, the indoor side lowers the temperature of the indoor

heat exchanger by means of the low-temperature low-pressure refrigerant, so that after

returning to the heating mode, the temperature decrease of the indoor heat exchanger acts

as a thermal mass to correspondingly delay the return to the heating mode. As such, the

efficiency is decreased by the defrosting operation in a conventional heat pump.

[Disclosure]

[Technical Problem]

The present invention aims to provide a heat pump which is high in thermal

efficiency and which prevents the occurrence of frost.

[Technical Solution]

One aspect of the invention provides a heat pump comprising a compressor,

which compresses a refrigerant to a high temperature and high pressure; an indoor heat

exchanger, which condenses the refrigerant compressed at the compressor; a

thermal-storage heat exchanger, in which heat is transferred to a heat medium from the

refrigerant leaving the indoor heat exchanger; a heat-medium heat exchanger, in which

the refrigerant, by evaporating, absorbs heat from the heat medium made to store heat by

the thermal-storage heat exchanger; a circulation device, which circulates the heat

medium between the thermal-storage heat exchanger and the heat-medium heat

exchanger; an outdoor heat exchanger, which absorbs heat from the exterior by

evaporating the refrigerant drawn out of the indoor heat exchanger; expansion valves,

installed at the inlets of the indoor heat exchanger and the outdoor heat exchanger, which

expands the refrigerant or the heat medium; a second control valve formed between the

outlet side of the thermal-storage heat exchanger and the inlet side of the outdoor heat

exchanger; and a first control valve formed between the outlet side of the thermal-storage

heat exchanger and the inlet side of the heat-medium heat exchanger.

When the temperature of the heat medium is below T ₂ , it may be preferable that

the circulation device be set to a halted state, and that the refrigerant drawn out of the

indoor heat exchanger be drawn into the outdoor heat exchanger by opening the second

control valve and closing the first control valve, and when the temperature of the heat

medium is equal to or above T ₂ , it may be preferable that the circulation device be

operated, and that the refrigerant drawn out of the indoor heat exchanger be drawn into

the heat-medium heat exchanger by closing the second control valve and opening the first

control valve and then be evaporated to receive heat from the heat medium.

It may be preferable that the heat pump further comprise a heat-medium valve,

formed between the outlet side of the compressor and the inlet side of the thermal-storage

heat exchanger, and a condenser valve, formed between the outlet side of the compressor

and the inlet side of the indoor heat exchanger. Here, when the temperature of the heat

medium is below T ₁ , the refrigerant drawn out of the compressor may be drawn into the

thermal-storage heat exchanger by opening the heat-medium valve and closing the

condenser valve and then may be drawn through the expansion valve into the outdoor

heat exchanger, and when the temperature of the heat medium is equal to or above T ₁ , the

refrigerant drawn out of the compressor may be drawn into the indoor heat exchanger by

closing the heat-medium valve and opening the condenser valve.

When the indoor temperature is equal to or above T ₃ , the heat pump may be set to

a stand-by state, and when the indoor temperature is below T ₃ , the refrigerant drawn out

of the compressor may be drawn into the thermal-storage heat exchanger and then may be

drawn through the expansion valve into the outdoor heat exchanger when the temperature

of the heat medium is below T ₂ , while the refrigerant drawn out of the compressor may be

drawn into the heat-medium heat exchanger when the temperature of the heat medium is

equal to or above T ₂ .

It may be preferable that the heat pump further comprise a heat-medium

measurement device, which measures the temperature of the heat medium; an indoor

measurement device, which measures the indoor temperature; and a control device,

which, when the indoor temperature recognized by the indoor measurement device is

equal to or above T ₃ , may keep the heat pump in a stand-by state, and which, when the

indoor temperature is below T ₃ , may open the second control valve to allow the

refrigerant to flow to the outdoor heat exchanger when the temperature of the heat

medium recognized by the heat-medium measurement device is below T ₂ , and may

operate the circulation device and open the first control valve to allow the refrigerant to

flow to the heat-medium heat exchanger when the temperature of the heat medium is

equal to or above T ₂ .

The heat medium may preferably be ethylene glycol, and it may be preferable

that trisodium phosphate (Na ₃ PO ₄ ) be added to the heat medium. It may be preferable that

the heat pump further include an oil separator between the outlet side of the compressor

and the inlet side of the indoor heat exchanger. It may also be preferable that the heat

pump further include a receiver formed at the inlet side of the compressor. Further, it may

be preferable that the heat pump further include a side glass formed between the inlet side

of the compressor and the receiver.

[Description of Drawings]

Fig. 1 is a diagram illustrating a conventional heat pump system.

Fig. 2 is a diagram of a heat pump system according to an embodiment of the

present invention.

Fig. 3 is a flowchart illustrating the operation of a heat pump according to an

embodiment of the present invention.

<Description of Reference Numerals for Key Components>

11 : indoor heat exchanger 13 : compressor

14: pressure gauge 15: thermal-storage heat exchanger

17: heat-medium heat exchanger 19: circulation device

21 : outdoor heat exchanger 23 : outdoor fan

25: receiver 27: side glass

29: oil separator 31 : first expansion valve

33: second expansion valve 35: overpressure breaker

37: first control valve 39: second control valve

41 : condenser valve 43 : heat-medium valve

[Mode for Invention]

Embodiments of the heat pump according to the invention will be described

below in more detail with reference to the accompanying drawings. In the description

with reference to the accompanying drawings, those components are rendered the same

reference number that are the same or are in correspondence regardless of the figure

number, and redundant explanations are omitted.

Fig. 2 is a diagram of a heat pump system according to an embodiment of the

present invention. The heat pump illustrated in Fig. 2 comprises a compressor 13 which

compresses a refrigerant (not shown), an oil separator 29 formed at the outlet side of the

compressor 13, a heat-medium valve 43 and a condenser valve 41 formed at the outlet

side of the oil separator 29, an indoor heat exchanger 11 connected with the condenser

valve 41 , a thermal-storage heat exchanger 15 connected with the heat-medium valve 43 ,

a heat-medium heat exchanger 17 at which the refrigerant receives heat from the heat

medium when the temperature of the heat medium is equal to or above a set value, a

circulation device 19 which circulates the heat medium between the thermal-storage heat

exchanger 15 and the heat-medium heat exchanger 17, a receiver 25 formed at the outlet

side of the thermal-storage heat exchanger 15, a first control valve 37 formed at the inlet

side of the heat-medium heat exchanger 17, an outdoor heat exchanger 21 located

outdoors, and a second control valve 39 located at the inlet side of the outdoor heat

exchanger 21. Also, the arrows in Fig. 2 depict the direction of flow of the refrigerant or

the heat medium.

The compressor 13 is located between a side glass 27 and the oil separator 29,

with a pressure gauge 14 installed on the inlet and outlet sides of the compressor 13 for

measuring the inlet pressure and outlet pressure, respectively. The compressor 13

compresses the refrigerant that has passed through the heat-medium heat exchanger 17 or

the outdoor heat exchanger 21, to create a high-temperature high-pressure vapor

refrigerant. Any of a variety of types of compressors may be used for the compressor 13

according to usage, such as a reciprocating type, swash plate type, swivel plate type,

rotary type, or scroll type, etc.

The refrigerant may be a refrigerant generally used in heat pumps, for example

R22, etc.

The side glass 27 is a device which examines whether or not there is any liquid

included in the refrigerant produced from the receiver 25, and the oil separator 29 is a

device which separates any oil that may be included in the refrigerant compressed by the

compressor 13. Also, the receiver 25 is a device which converts any liquid phase

refrigerant, that may be included in the refrigerant flowing to the compressor 13, into

vapor phase refrigerant. The side glass 27 and the receiver 25 improve the performance of

the compressor 13.

The heat-medium valve 43 is connected between the outlet side of the oil

separator 29 and the inlet side of the thermal-storage heat exchanger 15, while the

condenser valve 41 is connected between the outlet side of the oil separator 29 and the

inlet side of the indoor heat exchanger 11. When the temperature of the heat medium is

too low at the initial start-up of the heat pump, or when the indoor temperature has

reached the set heating temperature, the heat-medium valve 43 is opened while the

condenser valve 41 is closed, so that the refrigerant is made to flow only to the

thermal-storage heat exchanger 15. Also, when the heat-medium valve 43 is closed while

the condenser valve 41 is opened, the refrigerant flows only to the indoor heat exchanger

11.

The indoor heat exchanger 11 is connected between the condenser valve 41 and

the thermal-storage heat exchanger 15, releases heat from the high-temperature

high-pressure vapor refrigerant compressed by the compressor 13 to condense it into a

high-temperature high-pressure liquid refrigerant. Thus, the heat released when the vapor

refrigerant is changed into a liquid is transferred to the air of the indoor space, so that the

indoor temperature is raised. Although it is not illustrated, the indoor heat exchanger 11

may be of a typical type, which includes an inlet header and outlet header, a plurality of

tubes which connect the two to form a particular flow path, and corrugated heat fins

stacked between the tubes. Also, the indoor heat exchanger 11 may be equipped with an

additional cooling fan (not shown), where the air blown by the cooling fan passes the heat

fins between the tubes, so that the refrigerant flowing inside the indoor heat exchanger 11

loses heat to the blown air during this process and a condensing operation is performed on

the refrigerant.

The thermal-storage heat exchanger 15 is located between the outlet side of the

indoor heat exchanger 11 and the receiver 25, and inside the thermal-storage heat

exchanger 15 is formed a pipeline through which the heat medium (not shown) may flow.

Inside the thermal-storage heat exchanger 15, the heat medium receives and stores the

heat transferred from the high-temperature high-pressure liquid refrigerant leaving the

indoor heat exchanger 11. That is, when the temperature of the heat medium is below a set

temperature T ₂ , heat is stored in the heat medium using the high-temperature

high-pressure refrigerant leaving the indoor heat exchanger 11, in order to raise the

temperature of the heat medium to T ₂ or above. When the temperature of the heat medium

is equal to or above T ₂ , the circulation device 19 is operated, the first control valve 37 is

opened, and the second control valve 39 is closed, so that the refrigerant receives heat

from the heat medium in the heat-medium heat exchanger 17.

Since the heat medium stores the heat transferred from the high-temperature

high-pressure refrigerant leaving the indoor heat exchanger 11 , it may be preferable that a

fluid high in specific heat, e.g. ethylene glycol, be used. Also, it may be preferable to add

trisodium phosphate (Na ₃ PO ₄ ) to the ethylene glycol for increasing the liquidity of the

ethylene glycol. When the temperature of the heat medium is made to be T ₂ or above, due

to the storing of the heat emitted from the refrigerant drawn out of the indoor heat

exchanger 11, the heat medium is circulated by the circulation device 19 and transfers

heat to the refrigerant inside the heat-medium heat exchanger 17. At this time, the outdoor

heat exchanger 21 halts its operation.

Thus, embodiments of the present invention provide superior efficiency, as the

heat from the refrigerant drawn out of the indoor heat exchanger 11 is stored and reused

afterwards. Furthermore, the operation of the outdoor heat exchanger 21 is halted while

there is heat exchanged inside the heat-medium heat exchanger 17, and since the outdoor

heat exchanger 21 is not operated at times vulnerable to frost, the occurrence of frost is

prevented.

When the temperature of the heat medium is below T ₁ , for smoother functioning

of the heat medium, it may be preferable to close the condenser valve 41 and open the

heat-medium valve 43, in order to use the high-temperature high-pressure refrigerant

leaving the compressor 13 primarily for heating the heat medium. Them, when the

temperature of the heat medium is T ₁ or above, the condenser valve 41 is opened and the

heat-medium valve 43 is closed, for a normal heating operation.

Inside the heat-medium heat exchanger 17, heat is exchanged between the heat

medium, having a temperature of T ₂ or above, and the refrigerant. That is, heat is

transferred from the heat medium, which has been made to store heat by the

thermal-storage heat exchanger 15, to the refrigerant drawn in through the first control

valve 37. Here, the circulation device 19 circulates the heat medium between the

thermal-storage heat exchanger 15 and the heat-medium heat exchanger 17. A circulation

pump, etc., may be used for the circulation device 19.

A first expansion valve 31 is connected at the inlet side of the heat-medium heat

exchanger 17. The first expansion valve 31 rapidly lowers the temperature and pressure

of the refrigerant drawn in through the first control valve 37, to facilitate the evaporation

of the refrigerant inside the heat-medium heat exchanger 17. Although it is not illustrated

in detail, a thermal expansion valve may be used for the first expansion valve 31 , such as

an internal constant-pressure type, which regulates the route of the high-pressure

refrigerant's flow path, by means of a pressure transfer rod, through the expansion

displacement of a diaphragm according to the temperature inside a temperature sensing

unit, or an external constant-pressure type, which regulates the route of the high-pressure

refrigerant's flow path through the expansion displacement of a diaphragm, using

capillary tubes.

The refrigerant, after transferring heat to the heat medium at the thermal-storage

heat exchanger 15, is drawn in through the second control valve 39 to the outdoor heat

exchanger 21. At the outdoor heat exchanger 21, after the refrigerant is drawn in, which

has transferred heat to the heat medium at the thermal-storage heat exchanger 15, it is

evaporated, where the latent heat of evaporation is obtained by absorbing heat from the

exterior. When the temperature of the heat medium is below T ₂ , so that it is inefficient for

the heat medium to transfer heat to the refrigerant, the outdoor heat exchanger 21 absorbs

heat from the exterior and transfers it to the refrigerant. When the temperature of the heat

medium is T ₂ or above, the outdoor heat exchanger 21 halts its operation.

At the front of the outdoor heat exchanger 21 is located an outdoor fan 23, which

draws in outdoor air to the outdoor heat exchanger 21.

It takes about 30 minutes after operating the outdoor heat exchanger 21 for the

internal and external temperature difference of the outdoor heat exchanger 21 to reach 7

⁰ C or greater, which is the typical condition for frost to occur. Since the operation time of

the outdoor heat exchanger 21, i.e. the time it takes for the temperature of the heat

medium to rise from below T ₂ to T ₂ or above, corresponds to about 2 to 3 minutes, frost is

prevented on the outdoor heat exchanger 21.

A second expansion valve 33 is connected at the inlet side of the outdoor heat

exchanger 21. The second expansion valve 33 rapidly lowers the temperature and

pressure of the refrigerant drawn in through the second control valve 39, to facilitate the

evaporation of the refrigerant at the outdoor heat exchanger 21. The second expansion

valve 33 may be the same type of valve used for the first expansion valve 31.

The first control valve 37 is connected at the inlet side of the first expansion valve

31, and the second control valve 39 is connected at the inlet side of the second expansion

valve 33. When the temperature of the heat medium is T ₂ or above, so that there is heat

exchange inside the heat-medium heat exchanger 17, the first control valve 37 is opened,

and the second control valve 39 is closed. Also, when the temperature of the heat medium

is below T ₂ , so that the heat-medium heat exchanger 17 is not operated whereas the

outdoor heat exchanger 21 is operated, the first control valve 37 is closed and the second

control valve 39 is opened.

An overpressure breaker 35 is connected at the outlet side of the receiver 25,

where the overpressure breaker 35 measures the pressure of the high-temperature

high-pressure refrigerant leaving the indoor heat exchanger 11 and transfers it to a control

device (not shown).

Although it is not illustrated in Fig. 2, the heat pump system may further be

equipped with a heat medium measurement device, which measures the temperature of

the heat medium, and an indoor measurement device, which measures the indoor

temperature. Also, the heat pump system may additionally be equipped with a control

device which, when the indoor temperature recognized by the indoor measurement

device is T ₃ or above, halts the operation of the heat pump, and which, when the indoor

temperature is below T ₃ , opens the second control valve 39 and closes the first control

valve 37 so that the refrigerant flows to the outdoor heat exchanger if the temperature of

the heat medium recognized by the heat-medium measurement device is below T ₂ , and

operates the circulation device and opens the first control valve so that the refrigerant

flows to the heat-medium heat exchanger if the temperature of the heat medium is equal

to or above T ₂ . Such a control device measures the indoor temperature and the

temperature of the heat medium to generally control the operation of the heat pump.

The value T ₃ is a value for the desired indoor temperature setting, and may be set

by the control device. When the indoor temperature is below T ₃ , the control device

measures the temperature of the heat medium to start the heating operation of the heat

pump, and when it is T ₃ or above, the control device keeps the heat pump in a stand-by

state.

The value T ₂ represents a temperature at which it is suitable for the heat medium

to receive heat from the refrigerant inside the thermal-storage heat exchanger 15 and

transfer heat to the refrigerant inside heat-medium heat exchanger 17. The value T ₁

represents a standard temperature by which to determine whether or not the control

device will preliminarily heat the heat medium for smooth operation of the system, when

the temperature of the heat medium has been excessively lowered, for example, at the

initial operation of the heat pump or at an operation after a prolonged period of

non-operation.

The operation of the heat pump according to an embodiment of the invention will

be described below with reference to Fig. 3. Fig. 3 is a flowchart illustrating the operation

order of a heat pump according to an embodiment of the present invention.

First, the control device determines whether or not the indoor temperature is T ₃ or

above, and when it is T ₃ or above, halts the operation of the heat pump and sets it in a

stand-by state. When the indoor temperature is below T ₃ , the control device determines

whether or not the temperature of the heat medium is T ₁ or above.

When the temperature of the heat medium is below T ₁ , the control device opens

the heat-medium valve 43 and the second control valve 39, and operates the outdoor heat

exchanger 21. Thus, the heat medium absorbs heat from the high-temperature

high-pressure refrigerant leaving the compressor 13. Then, the control device

continuously measures the temperature of the heat medium to check whether or not the

temperature of the heat medium is T ₁ or above. When the temperature of the heat medium

is made equal to or above T ₁ , the control device opens the condenser valve 41, closes the

heat-medium valve 43 , operates the indoor heat exchanger 11 , and checks whether or not

the temperature of the heat medium is T ₂ or above.

A temperature of the heat medium below T ₂ means that the heat medium does not

have a sufficient amount of heat for heating the refrigerant. Thus, the outdoor heat

exchanger 21 is operated while the second control valve 39 is opened and the first control

valve 37 is closed, in order to store heat in the heat medium. Afterwards, the control

device proceeds to checking whether or not the indoor temperature is T ₃ or above.

A temperature of the heat medium equal to or above T ₂ means that the heat

medium has a sufficient amount of heat for supplying heat to the refrigerant. Thus, the

circulation device 19 and the heat-medium heat exchanger 17 are operated while the first

control valve 37 is opened and the second control valve 39 is closed, in order to transfer

the amount of heat stored in the heat medium to the refrigerant. Also, the control device

halts the operation of the outdoor heat exchanger 21. Then, the control device repeats the

step of checking whether or not the indoor temperature is T ₃ or above.

Here, since the refrigerant receives the stored heat from the heat medium, it is

possible to halt the outdoor heat exchanger 21, and when the heat medium stores heat

such that its temperature is kept at T ₂ or above, the outdoor heat exchanger 21 is halted,

whereas when the heat stored in the heat medium is transferred by the heat-medium heat

exchanger 17 to the refrigerant such that its temperature is below T ₂ , the outdoor heat

exchanger 21 is operated. Here, since the operation time of the outdoor heat exchanger 21

is shorter than the time required for frost to occur, the occurrence of frost is prevented on

the outdoor heat exchanger 21.

The composition and advantages of the heat pump according to an embodiment

of the invention will be examined below in greater detail with reference to experimental

results.

Experiment Conditions

A 5HP scroll compressor was used for the compressor 13, while three 9,600

Kcal/h class hot-water supply type fan heaters (power consumption 45 W) and a

hot-water circulation type motor (2,400 Kg/h) were used as the indoor heat exchanger 11.

Also, a heat-medium circulation type motor (6,000 Kg/h) was used for the circulation

device 19, and a 5HP class air-cooled type evaporator is used for the outdoor heat

exchanger 21. Further, a Yokogawa DA-series data module device was used for the

control device, while eight R-type temperature sensors were used as measurement

devices. The temperature sensors were installed at the inlet and outlet sides of the

compressor 13, indoor heat exchanger 11, heat-medium heat exchanger 17, and outdoor

heat exchanger 21.

The outdoor temperature condition was 0 to 3 ⁰ C, and the first expansion valve 31

and the second expansion valve 33 were of a capillary tube type. The time at which the

indoor temperature was normalized was selected as the point after 1 hour's operation of

the heat pump, i.e. the point at which the temperature of the hot water was 50 ⁰ C or higher,

and the temperature of the heat medium was measured at 40 to 45 ⁰ C. The outdoor heat

exchanger 21 was installed outdoors, with the distance to the indoor heat exchanger 11

being 3 m. The pressures P ₁ , P ₂ , P ₃ , and P ₄ lowered at the second expansion valve 33 were

measured after changing to a high pressure at a low temperature.

Experiment Results

The results measured by the above measurement devices are listed below in

Tables 1 to 4 in order of pressure decrease due to the second expansion valve 33.

[Table 3 ] Using P3 class Capillary Tube Expansion Valve

[Table 4] Using P4 class Capillary Tube Expansion Valve

There was no frost at all on the outdoor heat exchanger 21 , and in the mean heat

equation,

Q= m C _p δT

(where m: amount of hot water supplied to the indoor heat exchanger, C _p \ specific heat of

the hot water, λ T: temperature difference of the hot water between the inlet and outlet) m

= 2400 kg/h, C _p = 1 kcal/kg-°C, and AT= 7.85 ⁰ C (the mean value of heating differences

shown in Tables 1 to 4). The amount of heat supplied to the indoor heat exchanger, by the

above equation, is 18,852 kcal/h, and the power consumption of the heat pump is on

average 4.6 kWh, i.e. 3,956 Kcal/h (heat use = power use x 860 Kcal/kWh), so that

coe «ff:ici•en ₊ t o *r• per *fo■ rmance = 1.8 _6„5_2. k —cd TlJ/Tk ^{~ =} 4 ,- _7 _ώ 6

Thus, a heat pump according to embodiments of the present invention has a substantially

higher efficiency, compared to the thermal efficiency of a typical commercial heat pump

of about l.2 to 3.3.

While the spirit of the invention has been described in detail with reference to

particular embodiments, the embodiments are for illustrative purposes only and do not

limit the invention. It is to be appreciated that those skilled in the art can change or modify

the embodiments without departing from the scope and spirit of the invention. For

example, it is apparent that the heat pump can be made to perform a cooling function by

reversing the flow of the refrigerant.

[Industrial Applicability]

According to the present invention set forth above, a heat pump maybe provided

which is high in thermal efficiency and which prevents the occurrence of frost.