DE4001525A1 - HEAT PUMP FOR THE SAME DELIVERY OF COLD AND HOT FLUIDS - Google Patents

Abstract

A heat pump capable of simultaneously supplying cold and hot fluids comprises a refrigeration cycle including a compressor 1, a condenser 2, an evaporator 4 and expansion valves 3; a path for a fluid to be heated connecting from a feed inlet 15 of the fluid via the condenser to a hot-fluid outlet 12; and a path for a fluid to be cooled connecting from a feed inlet 16 of the fluid via the evaporator 4 to a cold-fluid outlet 13. A refrigerant liquid-gas heat exchanger 11 is interposed in the refrigeration cycle to cause heat exchange between the liquid refrigerant and gaseous refrigerant in countercurrent flow. Both paths for the fluid to be heated and the fluid to be cooled are constituted as a once-through path. In the condenser, the refrigerant and the fluid to be heated are passed in countercurrent flow. Thus, a short rise time of operation, and a higher-temperature hot fluid and a lower temperature cold fluid than usual are obtained. <IMAGE>

Description

The invention relates to a heat pump for simultaneous delivery of cold and hot fluids, in particular to a heat pump that allows one to gain much hotter fluid and to to shorten the time available to him.

The predominant hot water utility heaters include electric heaters and hot water boiler. Their operating costs, however, are high, being particularly the hot water boiler because of the exhaust gases Environmental pollution problem. Accordingly, the existing equipment corresponded not always the current social Requirements that a clean energy too low Charge costs.  

So are heat pumps as hot water supply systems at low cost and pollutant free in the Foreground stepped. Recently, because of the simultaneous use as a refrigerator Variety of heat pumps commercially available to the simultaneous delivery of cold and warm water allow.

An example of such a known heat pump is shown in Fig. 3, in which a compressor 1 , a condenser 2 , an expansion valve 3 and an evaporator 4 form a cooling circuit. On the condenser side, a recirculation line for water to be heated is connected to a hot water tank 5 'and has a water pump 9 and a valve 7 . On the evaporator side, a recirculation line for the water to be cooled is connected to a cold water tank 6 'and also has a water pump 10 and a valve 8 .

The cooling circuit of the known heat pump constructed in this way, which simultaneously supplies cold and hot water, can be represented in a Mollier diagram according to FIG. 4, in which the symbols "i" and "p" denote the enthalpy values and the pressure values, respectively. From the Mollier diagram the following is apparent: Originally, initially, in the compressor 1, the refrigerant is pressurized and compressed, at which stage there is an enthalpy change from i ₁ to i ₂ ; Subsequently, in the condenser 2, the gaseous refrigerant is cooled by the heat exchange with the water to be heated and liquefied at a constant pressure until it passes into the supercooled state i ₃ ; Then, the liquid refrigerant enters the expansion valve 3 , in which it adiabatically expands to the state i ₄ , which corresponds to the same value as i ₃ ; Thereafter, the refrigerant in the evaporator 4 absorbs heat by heat exchange with the water to be cooled, whereby it is gasified at a constant pressure and becomes the superheated state i ₁ , which deviates from i ₁ without returning to the initial value i ₁ .

Accordingly, each of the hot water tank 5 'and the cold water supply tank 6 ' are arranged on the condenser side and on the evaporator side, wherein water in the cold water tank 6 'is circulated by means of the water pump 10 for heat exchange with the gaseous coolant. Accordingly, when accompanied by an increased condensation temperature, the condensing pressure increases, so that hot water is recovered while the evaporation pressure is lowered, accompanied by a decrease in the evaporation temperature, thereby generating cold water. In the course of these state changes, the Mollier diagram shifts gradually in the course of the operation time in the direction of the ordinate axis, as from the transitions

i ₁ → i ₁ '→ i ₁'', i ₂ → i ₂' → i ₂ '',

i ₃ → i ₃ '→ i ₃'', i ₄ → i ₄' → i ₄ '',

is apparent, so that as a result a lower COP value (efficiency) is achieved.

The COP value of the Mollier diagram shown in FIG. 4 is defined by the following equation:

As you know, the COP gives a heat pump the thermal efficiency of the associated system again and its height affects the final temperatures of the obtained cold and hot water.

It is clear from the above equation that to improve the COP it is necessary to increase the expression ( i ₂ " -i ₃ "), ie the enthalpy difference on the capacitor side, and also the expression ( i ₂ "). i ₁ ''), ie the working equivalent of the compressor 1 .

So far, a number of measures have been taken for this purpose to improve the thermal efficiency of the condenser 2 and / or the evaporator 4 , for example by increasing their heat exchange surfaces, by increasing the enthalpy difference between the supercooled and superheated areas by means of heat exchange between the liquid coolant at the Accordingly, existing heat pumps which simultaneously supply hot and cold water have a COP of 4.0 and finally produce hot water of about 75 ° C.

However, the aforementioned known heat pump of the same kind as that of the invention requires a long build time (increase in time), since the water to be heated with the help of the water pump 9 of the hot water supply tank 5 'is circulated. In other words, a predetermined hot water temperature is achieved only in the course of regenerating the heat of the condenser 2 in the hot water supply tank 5 '. Moreover, the pump is not able to produce even with the aforementioned measures hot water of more than 75 ° C. In a circulating system in which the water to be heated is heated while circulating, it is impossible to raise the water temperature at one time; and when the water temperature has been raised to the definite temperature during the operating time, the logarithmic mean temperature difference between the water and the refrigerant in the condenser will be small. In particular, when the logarithmic mean temperature difference is below a certain value, the circulation does not provide a sufficient amount of heat for the exchange, so that the refrigerant no longer condenses. The temperature rise stops so. An increased compression ratio and a reduced COP are the consequence accordingly.

In such a state reached, the combined Use of the aforementioned electric heater, Hot water boiler etc. inevitable, so that the Problems of high cost and pollution are still unavoidable.

To cope with the current situation, the present invention was made with the aim of to improve the COP of a heat pump in the Location is at the same time hot and cold fluids too deliver. The main object of the invention is a high temperature fluid greater than 75 ° C in one extremely short time to win.

According to the present invention, which is the meets the aforementioned objective, becomes a heat pump created simultaneously hot and cold fluids supplies, wherein the pump has a cooling circuit, a compressor, a condenser, relaxation valves and having an evaporator, and wherein the Cooling circuit comprises the following components: One Liquid-gas heat exchanger for the coolant for Inducing a heat exchange between a liquid coolant from the exit of the Condenser flows to the expansion valves, and a gaseous coolant from the evaporator to Compressor flows, the heat exchanger in the Middle between a connection path from the condenser to  the expansion valves and a connection path from Evaporator is arranged to the compressor and to serves the liquid and the gaseous coolant to undergo a heat exchange in countercurrent; a disposable flow path for the fluid to be heated, the feeding of the fluid source over the Capacitor with the supply outlet of the hot Fluids connects; and a disposable passageway for the to be cooled fluid, the food intake of the Fluid source via the evaporator with the Supply outlet of the cold fluid connects, wherein said capacitor is such that it the coolant and the fluid to be heated in Pass countercurrent.

The term "fluid" as used herein means mainly water, but not limited thereto and also includes air and other substances. The For the sake of simplicity, the following is the expression Water used instead of fluid.

The present invention makes it possible to simultaneously but not to win cold and hot water exclude the possibility but only involve to use cold or warm water.

The flow method used in the invention differs from the known ones Circulation method in which the heated or water to be cooled at a predetermined temperature achieved during circulation. The pass method  is characterized in that the water through the Condenser or evaporator is directed where it is on once reached a predetermined temperature and in This condition is delivered to the user side.

According to a preferred embodiment of the heat pump According to the present invention, the capacities of the Capacitor and the evaporator so enlarged that they have a sufficient heat exchange for Delivery of a hotter hot water or one Allow colder cold water.

Since the liquid coolant at the exit side of the Condenser and the gaseous coolant at the Outlet side of the evaporator with the help of Liquid-gas heat exchanger for the coolant Heat exchange in countercurrent process are exposed, are used in the present invention built and at the same time cold and hot water supplying heat pump the liquid refrigerant, the already at a higher temperature in the supercooled state is located, and the gaseous Coolant that is at a low temperature in the Overheating condition is to replace the Heat causes, causing the liquid coolant cooled and further subcooled while the heated gaseous coolant and further overheated becomes.

Time before this heat exchange is in the condenser the water to be heated, in countercurrent to the  Coolant, supplied in a one-pass process, so that always fresh feed water into the condenser flows, creating a more effective supercooling of the Coolant on the outlet side favors and a large logarithmic mean temperature difference between the feed water and the coolant is maintained.

On the other hand, also in the evaporator feed water in One-pass procedure forwarded to it possible, a high logarithmic mean Temperature difference between the feed water and the Maintain coolant.

In this way, by favoring the Hypothermia and overheating in the Coolant circuit the enthalpy difference between increases the capacitor side and the evaporator side, while by maintaining a high logarithmic mean temperature difference that Compression ratio is minimized. As a result of the the associated synergy effect will be the COP improved and adequate heat exchange achieved. Accordingly achieved in the heat pump according to the present invention, the water to be heated when flowing through the capacitor once higher temperature and thus becomes one High temperature water for hot water consumption.

Hereinafter, the subject matter of the description The figures belonging to the invention are specified.  

Fig. 1 is a schematic system diagram showing an example of a simultaneous supply heat pump and cold and hot fluid according to the present invention;

FIG. 2 is the Mollier diagram of the heat pump shown in FIG. 1; FIG.

Fig. 3 is a similar system diagram of a known heat pump of the same type;

Fig. 4 illustrates the Mollier diagram of the known heat pump shown in Fig. 3; and

FIG. 5 to FIG. 8 illustrate graphs of the one-pass process used in the present invention as compared with the conventional recirculation method, with respect to the hot water outlet temperature (condenser side), the COP value (condenser side), the cold water outlet temperature (evaporator side), and FIG COP value (evaporator side), in each case related to the elapsed operating time.

Hereinafter, an embodiment of the invention will be described with reference to FIG . Referring to Fig. 1, a refrigerant path is created by connecting pipes as follows: from the exit side of the compressor 1 through the condenser 2 into the liquid-gas heat exchanger 11 for the refrigerant and further to the expansion valves 3 ; then through the evaporator 4 back into the heat exchanger 11 and from there to the inlet side of the compressor 1 , whereby the coolant circuit is complete.

As for the way of the water to be heated, a disposable flow path is provided in such a way that piping, starting from a feed head 15 through the condenser 2 in countercurrent to the coolant path, then via a valve 7 to the hot water supply tank 5 and a hot water supply head 12 arranged parallel thereto connected with each other.

Concerning the path of the water to be cooled, a disposable flow path is provided in which piping runs from a supply head 16 for fresh water to the evaporator 4 and further to the valve 8 and the cold water tank 6 as well as to a supply outlet or faucet 13 arranged parallel thereto be connected to each other.

In the evaporator 4 according to FIG. 1, the flows of the coolant and of the water to be cooled are parallel flows, in contrast to the situation in the condenser 2 . But they can also be performed in the evaporator as countercurrent as in the case of the capacitor 2 .

As for the condenser 2 and the evaporator 4 , each has a larger capacity than usual and serves to achieve a thorough condensation and evaporation in order to achieve the intended temperatures of the high-temperature water and the cold water. As for the expansion valves 3 , one of them has a high flow rate and is concomitantly used to fully achieve the adiabatic expansion of the liquid coolant.

On the basis of the Mollier diagram shown in Fig. 2, the operation of the thus constructed, simultaneously cold and hot water supplying heat pump will now be described.

With the aid of the compressor 1 , the gaseous coolant is subjected to adiabatic compression, in which the enthalpy of i ₁ 'increases to i ₂ '. In the subsequent condenser 2 , the refrigerant is subjected to the heat exchange with the water to be heated, whereby it is cooled at a constant pressure and transferred to a liquid coolant. This is further cooled to the supercooled state i ₃ . Since the path of the water to be heated, as stated above, designed according to the one-pass process and the water to the coolant in countercurrent heat exchange, the water, which is always freshly fed, cools the coolant, whereby the logarithmic mean temperature difference between the two media is kept at a high constant value. At the same time, the water to be heated flows at normal temperature to the exit side of the condenser 2 where the refrigerant exits, and causes the heat exchange with the refrigerant, thereby making the supercooling more effective.

The liquid refrigerant in the enthalpy state i ₃ flows to the liquid-gas heat exchanger 11 for the refrigerant, where it is cooled by the gaseous refrigerant coming from the evaporator 4 , whereby the already in the supercooled state coolant is further cooled to the enthalpy state i ₃ '.

Then the coolant passes through adiabatic relaxation in the expansion valve 3 in the enthalpy i ₄ 'on. The refrigerant is then sent to the evaporator 4 , where it absorbs the latent heat by heat exchange with the water to be cooled and converts it into a gaseous refrigerant at constant pressure and overheats to the state i ₁ . In the evaporator 4 , the water to be cooled in the one-shot process enables the maintenance of a large logarithmic mean temperature difference between the gaseous and liquid refrigerants. The gaseous coolant re-enters the liquid-gas heat exchanger 11 for the coolant and is heated there by the liquid coolant coming from the condenser 2 , its overheating range being extended to the enthalpy state i ₁ '.

Thus, on the one hand, by constantly maintaining the logarithmic mean temperature difference between the condenser side and the evaporator side at a high value, the compression ratio of the compressor 1 is maintained at a low value, while on the other hand, by increasing the enthalpy difference between the supercooling and superheating regions, the enthalpy difference between the condenser side and the condenser Evaporator side is increased. In this situation, the COP is represented by the following equation:

For relations:

( i ₂ '- i ₃) <( i ₂ - i ₃); ( i ₁ - i ₄ ') <( i ₁ - i ₄).

The difference between ( i ₂ '- i ₁ ') and ( i ₂ - i ₁ ) is imperceptible, because at ( i ₂ '- i ₁ ') the compression ratio is kept small.

From this context it follows that the COP is improved, which means an increased thermal efficiency. Accordingly, the water to be heated is transferred to high temperature water in a short time as it flows through the condenser 2 ; and it is then stored in a hot water supply tank 5 or delivered directly to the supply outlet 12 for use. Accordingly, the water to be cooled is transferred to cold water in a short time as it flows through the evaporator 4 ; and it is then stored in the cold water tank 6 or delivered directly to the supply outlet 13 for use.

The heat pump according to the present Embodiment was under performance tested following conditions:

Compressor | 5,5 KW Heat transfer surface of the capacitor 0.42 (m² / a single heat pipe) × 2 = 0.84 m² Heat transfer surface of the evaporator 0.55 (m² / a single heat pipe) × 2 = 1.10 m² Heat transfer surface of the liquid-gas heat exchanger for the coolant 0.15 m² coolant Fron R 12 (trade name of dichlorodifluoromethane)

When water to be cooled and heated of 20 ° C each from respective feed stations 15 , 16 was fed and the compressor 1 was running, high temperature water of 90 ° C at the hot water supply head 12 or at the tank 5 and cold water at 6 ° C at the cold water supply head 13 or at the tank 6 provided. The temperature and pressure values were measured at both terminals of each of the condenser 2 , the evaporator 4, and the liquid-gas heat exchanger 11 for the refrigerant. Then the enthalpy was calculated. The COP was calculated according to the Mollier diagram shown in FIG .

The COP value is significantly larger than that conventional value of 4.0, which proves that the thermal efficiency has been improved.

Next, a comparison was made between the One-time flow type of heat pump according to the  present invention and a conventional Circulation type of heat pump, the Exit temperature of the hot water supply and the COP (both on the capacitor side) and the Outlet temperature of the cold water supply and the COP (both on the evaporator side) against the elapsed operating time were recorded. The Comparison results are in the following Tables 1 and 2 reproduced.  

Table 1

Elapsed operating time based on the outlet temperature of the hot water supply and the COP (condenser side)

Table 2

Elapsed operating time based on the outlet temperature of the cold water supply and the COP (evaporator side)

These comparative data were also recorded in waveform and are shown in Figs. 5, 6, 7 and 8, in which the round marks (○) indicate the disposable flow type and the square marks () indicate the conventional circulation type.

In the measurement were used: A C-C (Copper-constantan) thermocouple thermometer for Measuring the temperature; a Rotamesser for measuring the Discharge amounts of cold and hot water; on Bourdon pressure gauge for measuring condensation gas pressure and the evaporation gas pressure; and a Clamping Wattmeter for measuring power consumption of the compressor.

In the conventional circulation heat pump, about 95 liters of water were filled in the hot water tank 5 'and about 105 liters of water in the cold water tank 6 ', wherein the corresponding circulating amounts of cold and hot water 2500 liters / hour.

In the disposable heat pump was the Hot water outlet amount 180 liters / hour and the Cold water outlet amount 500 liters / hour.

As can be seen from Table 1, the Continuous heat pump on the condenser side the local water temperature of 20 ° C after 6 minutes immediately raised to 80 ° C and more, and after 40 minutes further to 100 ° C. Regardless of the strong Increase in the hot water supply temperature was the  COP value stable, without reduction, at high levels held.

In contrast, with the recirculating heat pump, it was not possible to produce hot water in excess of 75 ° C, with the COP decreasing as the hot water supply temperature rises. When trying to obtain hot water at a temperature of over 75 ° C, the condensation pressure of the refrigerant in the condenser exceptionally increased so much (over 30 kg / cm ² ) that a high pressure shutdown safety switch and the heat pump functioned put out of service.

On the other hand, the above Table 2 shows for the Evaporator side clearly that at the One-time heat pump water from 18 ° C to 2 minutes immediately cooled to 7 ° C, wherein then cold water of 6 ° C constantly delivered has been. The COP was continuous during the operating time held at high levels.

With the circulating heat pump, however, the Supply outlet temperature of the cold water through Forced circulation of water in the cold water tank be lowered, but with the falling of the Output temperature also decreases the COP value. As the Cold water outlet temperature reached 5 ° C, was the Operation interrupted to prevent the water in the evaporator to freeze.  

From the above comparison shows that a Circulating heat pump generally has the following defects:

• i) For a required cold water and a required To reach hot water temperature will be a long time Construction time (rise time) needed.
• ii) hot water with a Supply outlet temperature of 75 ° C or more can not be won.
• iii) A cold and a hot water tank are for Feeding fresh water, delivering and Saving the circulating water and to Heat storage indispensable.
• iv) The larger the temperature difference between the outlet temperatures of the hot water or Cold water supply of the initial Water inlet temperature is, more so the COP decreases.

The disposable heat pump according to the present The invention is in terms of the following features of Advantage:

• 1) The rise time to reach a required Hot water or cold water temperature is very high short. When the rise time has expired, stands the required hot water or cold water immediately available.  
• 2) It can be hot water with a Supply outlet temperature of 90 ° C or be provided more.
• 3) A cold water or hot water tank for Saving the flow water are not necessary components of the heat pump, so that they can be waived, depending on the Consumption intentions.
• 4) Cold water and hot water can over the course of Operating time to be delivered steadily, with the COP is kept stable at high levels.

Accordingly, it allows the Disposable heat pump according to the present Invention, all the shortcomings of the conventional To overcome and improve circulation heat pumps. Continue can be recovered high-temperature water, so that the area of application and use of the pump is expanded, resulting in significant, large Beneficial effects leads.

The above description refers to a Embodiment in which simultaneously cold water and Hot water is delivered. But it is of course according to the present invention possible, only a single To deliver water type. As described, the creates present invention, a heat pump, in which a Liquid-gas heat exchanger for the coolant for Inducing the heat exchange between one  liquid coolant of high temperature at the Exit side of the condenser and a gaseous Low temperature coolant at the exit side of the evaporator in the coolant circuit is turned on. In the condenser, the im One-pass process dispensed to be heated Water and the coolant heat exchange in the Countercurrent, while in the evaporator, the in One-shot procedure dispensed Water and the coolant heat exchange in the Parallel current can be performed. Create accordingly these so combined features a synergy effect, so that a significant improvement in the COP achieved becomes.

Specifically, the increase in enthalpy increases difference between the subcooling area and the overheating area, and securing the logarithmic mean temperature difference the COP, so that the hot water outlet temperature becomes higher. The one-time process enables delivery of high temperature and cold water in very short time.

The protection of the logarithmic middle Temperature difference prevents the increase of the Compression ratio of the compressor, so that the Compressor capacity can be small. This further reduces operating costs.

The simultaneously supplying cold and hot water  Heat pump according to the present invention allows So it, such a low tempered cold water and to produce such a high-temperature hot water, as so far in such an extremely short time not was possible. For example, hot water can be instant also at midnight, at a cheap night tariff become. Next it can be used immediately or in A tank will be stored to the electricity reduce consumption.

The heat pump is thus the current requirements and aspirations for low cost and cleaner Energy adapted and has an inherent environmentally friendly character.

Claims (6)

A heat pump for simultaneously supplying cold and hot fluids, comprising a refrigeration circuit having a compressor, a condenser, expansion valves and an evaporator,
characterized in that the cooling circuit comprises the following components:
a heat exchanger for effecting a heat exchanger between a liquid refrigerant flowing from the outlet of the condenser to the expansion valves and a gaseous refrigerant flowing from the evaporator to the compressor, the heat exchanger being in the middle between a connection path from the condenser to the expansion valves and a communication path from the evaporator to the compressor and serves to countercurrently heat exchange the liquid refrigerant and the gaseous refrigerant;
a disposable flow path for the fluid to be heated, which connects the feed inlet of the fluid source via the condenser with the supply outlet of the hot fluid; and
a disposable flow path for the fluid to be cooled, which connects the feed inlet of the fluid source via the evaporator with the supply outlet of the cold fluid;
wherein the condenser is such that the coolant and the fluid to be heated pass it in countercurrent. 2. Heat pump according to claim 1, characterized in that the Evaporator and the condenser one each Have heat exchange capacity more than twice as large as in the case that one normal cooling circuit with a Temperature difference between the coolant and any fluid from 10 ° C to 20 ° C below Operation of the compressor is operated. 3. Heat pump according to claim 1, characterized in that the Evaporator is designed so that it to be cooled fluid and the coolant in Pass parallel current. 4. Heat pump according to claim 1, characterized in that the Evaporator is designed so that it to be cooled fluid and the coolant in Pass countercurrent.   5. Heat pump according to claim 1, characterized in that each of the supply outlets of the hot fluid and the cold fluid from an outlet member consists. 6. Heat pump according to claim 5, characterized in that the Supply outlets of the hot fluid and the cold fluids include a supply tank, which is arranged parallel to the supply organ.