JP2728207B2 - Cooling medium condensation promotion method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a refrigeration system using a refrigerant compression-type and heat-drive-type cycle, by improving the heat radiation capacity and suppressing the cooling capacity from decreasing. The present invention relates to a method for operating a machine smoothly, and it can be suitably used for a refrigerator installed in a movable body such as an automobile, a train, a ship, or a fixed facility such as a house, an office, or a factory.

2. Description of the Related Art A refrigerator using a refrigerant compression type and a heat driven type cycle, a so-called compression refrigerator, is a compressor for compressing refrigerant vapor evaporated from an evaporator, and a refrigerant compressed by the compressor. It is composed of a condenser for cooling and condensing the vapor, an expansion valve for sending the condensed liquid refrigerant to a low-pressure evaporator in an appropriate amount, and an evaporator for evaporating the liquid refrigerant and cooling the surroundings. . By the way, in the above-mentioned condenser, it is necessary to continuously remove the heat generated during the liquefaction of the refrigerant. A water-cooled type that removes heat by using a temperature difference between water and a water temperature, and an air-cooled type that uses air instead of water are known.

However, the water-cooled type requires constant circulation of a large amount of water, which inevitably increases the size of the entire equipment.
It is inconvenient to attach to a moving object such as a train. As an improvement over the water-cooled type, there has been proposed a so-called evaporative type in which water is supplied to a heat radiation surface in a thin film form and the refrigerant is cooled by utilizing the steam heat of water. In this case, the theoretical amount of water used should be about several percent compared to the water-cooled type. However, in practice, the heat radiation surface must always be covered with a water film, and the amount of evaporated water must be replenished. For,
It has the disadvantage that it cannot be reduced so much and that the impurities in the water are concentrated as it evaporates, which leads to undesired situations such as corrosion and contamination of the contact surfaces, so that the water must be changed from time to time.

For the above reasons, most of the compression refrigerators currently used are air-cooled except for some industrial ones.

Meanwhile, the air-cooled condenser, has the heat radiation portion for heat exchange with air, generally for heat transfer coefficient of this part is low and ^{10~30kcal / m 2 · hr · ℃} , plate type Alternatively, corrugated fins are provided to increase the contact area with air. However, the capacity of the refrigerator has increased,
In order to cope with an increase in the amount of heat radiation, it is necessary to provide a larger fin and further increase the size of the blower so that the flow velocity of the air supplied to this portion can be sufficiently increased. In relation, it naturally has its limits.

On the other hand, if the ambient conditions of the air-cooled condenser exceed the permissible limit of the capacity of the condenser, for example, the air temperature rises,
If the temperature difference between the refrigerant and the air becomes smaller and it becomes impossible to follow the removal of the heat required for the condensation of the refrigerant, the inside of the condenser will reach a critical state even when the condenser is operated, and the normal refrigerant liquefaction will occur. No, resulting in loss of cooling capacity of the refrigerator. Especially in the case of moving objects such as automobiles and trains, it is difficult to always place the condenser in a condition within its capacity limit, for example, only in a shaded or well-ventilated place. Then 50% of the design value
Such situations are often encountered. Further, as a result of an increase in the refrigerant pressure due to an increase in the heat radiation temperature, a pressure exceeding the safety limit of the refrigerator may be generated, and the safety device may be activated to stop the operation.

As a method for preventing such a decrease in the heat exchange capacity of the compression refrigerator, it has been proposed to spray fine droplets on the outdoor exchanger, that is, to use the above-mentioned evaporative condenser (particularly). Japanese Patent Publication No. 60-40583).

However, simply spraying liquid droplets on the heat transfer surface creates a thick liquid film on the heat transfer surface due to excessive liquid spray, and despite the fact that the liquid evaporates to promote heat dissipation of the condenser, Since heat from the part is exchanged from the heat transfer surface side of the liquid film, evaporation will occur from the opposite side of the liquid film from the air side, in which case the presence of the liquid film will inhibit evaporation . Further, since heat exchange with air becomes difficult due to the presence of the liquid film, there is a disadvantage that merely spraying the droplets lowers the heat radiation effect of the condenser. In addition, spraying of excess liquid that cannot be completely evaporated in the heat radiating section always causes a state in which the condenser is wetted, and also causes a problem that liquid moisture droplets adhere to the inside of the device together with air, and the refrigerator has a problem. May cause a malfunction. In the case of an air-cooled heat exchanger, the only difference is whether the medium to be cooled is condensed or cooled, and the same phenomenon as in the case of the condenser occurs with respect to heat radiation on the air side.

SUMMARY OF THE INVENTION The present invention overcomes the aforementioned disadvantages of conventional air-cooled condensers, and under ambient conditions that exceed their capacity,
It is an object of the present invention to provide a simple cooling promoting method for exerting a function smoothly.

Means for Solving the Problems The present inventors have conducted various studies on a method of preventing a functional deterioration of a compression refrigerator, particularly a compression refrigerator having an air-cooled condenser, due to a change in ambient conditions. When the temperature reaches the liquefaction limit temperature of the refrigerant, an appropriate amount of water is supplied to the heat dissipating part together with air in the form of a spray at intervals capable of evaporating continuously and vaporized on the heat dissipating part surface. It has been found that the purpose can be achieved by using the latent heat of evaporation to bring the internal temperature below the critical value, and the present invention has been accomplished based on this finding.

That is, when operating the air-cooled condenser of the refrigerator having the heat radiating part, the present invention forms a liquid film on the heat radiating part surface when the temperature in the condenser reaches the liquefaction limit temperature of the refrigerant. By supplying the water that can evaporate in 0.1 to 2 seconds as fine droplets along with the air and utilizing the latent heat of evaporation of water and the sensible heat of the air, the temperature inside the condenser is reduced A method for accelerating the condensation of a cooling medium, characterized by performing a process of lowering the temperature to below the liquefaction temperature, and performing the process at a time interval at which water supplied with the process can always maintain an evaporating state on the surface of the radiator. is there.

In the method of the present invention, the supply amount of water needs to be an amount capable of evaporating in 0.1 to 2 seconds without forming a liquid film on the surface of the heat radiating portion. Into the water, a heat transfer promoter, an evaporation promoter, a cleaning agent, a rust inhibitor, and the like can be added as required to promote vaporization or prevent corrosion and contamination of equipment.

According to the method of the present invention, when an optimal amount of water is sprayed and the latent heat of evaporation of the water is used, the latent heat of evaporation is 560 kcal / kg, which is much larger than that of air. Can be compensated for, and since water evaporates at a constant temperature, the temperature of the heat radiating section can be reduced, and a decrease in cooling capacity due to an increase in air temperature can be avoided. Further, the lowering of the heat radiation temperature makes it possible to lower the operating pressure of the refrigerant, which leads to the normal operation of the refrigerator and the improvement of the performance on the refrigeration cycle.
Also, depending on the entrainment with the air, the water evaporates in the air before entering the condenser, thereby lowering the temperature of the air, and the heat transfer during the evaporation of the water sprayed to the heat radiating portion. The coefficient is more than 100 times that of air,
It has been found that the cooling capacity can be improved by improving the heat transfer characteristics in the heat radiating section. In this case, the relationship between the amount of water sprayed, the amount of heat exchange with air, and the amount of refrigerant condensed is expressed by the following equation.

ΔHc · Wc · (1−x) = Ca · Wa · Δta + y · ΔHw (1) ΔHc: Latent heat of condensation of refrigerant [kcal / kg] Wc: Flow rate of refrigerant [kg / hr] x: Dryness [−] Ca : Specific heat of air [kcal / kg · ° C] Wa: Air flow rate [kg / hr] Δta: Temperature difference between inlet and outlet of air in condenser [° C] y: Sprayed amount of water [kg / hr] ΔHw: Evaporation of water Latent heat [kcal / kg] When water is not sprayed, y · ΔHw in the second term on the right side of the above equation
When the temperature difference with the refrigerant decreases due to the increase in the air temperature, heat exchange with the air is not sufficiently performed, and Δ
ta decreases, and as a result, the dryness x of the refrigerant increases. An increase in x means that the refrigerant does not completely condense, and the cooling capacity in this case decreases.

In addition, in the case of a mobile type such as a vehicle-mounted type, the cooling air flow rate Wa differs between when the vehicle is running and when the vehicle is stopped, and when the vehicle is stopped, the dryness x increases because the Wa decreases. On the other hand, in the method of the present invention, water is sprayed to the condenser together with air at a time interval capable of always maintaining an evaporating state, and the latent heat generated when the sprayed water evaporates is used to make Δta or Wa This is intended to prevent the increase in the dryness x due to the decrease in the dryness, promote the liquefaction of the refrigerant in the condenser, and bring the dryness close to zero. Therefore, there is an optimum condition for setting the degree of dryness to 0 for the spray amount y of water. If the amount of sprayed water becomes more than the optimal value by spraying water constantly to the condenser as before, liquid that cannot be evaporated remains on the heat dissipation surface of the condenser, and the liquid is thick The formation of the liquid film impedes the heat exchange with the air and the preferable evaporation of the liquid from the heat dissipation surface side. However, according to the present method, such a phenomenon does not occur.

The spraying of water in the method of the present invention is characterized in that the next spraying is carried out at the same time that the moderately sprayed water evaporates from the heat radiation surface, thereby attempting to radiate heat in the most effective condenser, Therefore, water spraying is performed at appropriate intervals. Here, the relation between the spraying amount and the spraying interval is as follows: y: Spraying amount [kg / hr] A: Heat transfer area of heat radiating part [m ² ] t: Thickness when sprayed liquid adheres to heat radiating part [m] ρ: Liquid density [kg / m ³ ] θ ₁ : time required for spraying [sec] θ ₂ : time required for evaporation of water [sec] For example, in refrigerators for automobiles, home-room cooling, etc., θ ₂ is 0.1 to ₂ seconds, and y is the unit of the radiator. About 10 to 100 mg per area (cm ² ) is appropriate.

Embodiment Next, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory view showing an example of an embodiment of the method of the present invention, in which a fine liquid of water generated by a nozzle 4 is supplied to a heat radiating portion of an air-cooled condenser composed of a condenser 1 and a heat radiating portion 2 thereof. Blower 3 for drops
It is supplied together with the air sent from. This water is sent from a tank 6 to a nozzle 4 by a pump 5, and the supply of water to the nozzle 4 is controlled by a timer 7.

The refrigerant A is condensed in the condenser 1, sent to the evaporator 9 via the expansion valve 8, and vaporized. In general, the air-cooled type has a low heat exchange capacity between air and a refrigerant. Therefore, a method has been adopted in which fins are attached to the heat radiating section 2 and the capacity of the blower 3 is further increased to increase the amount of air. In this case, the capacity of the condenser including the blower becomes large, and in addition, when the air temperature rises, the amount of heat exchange in the heat radiating portion is greatly reduced. As an improvement method, there is a method in which the water filled in the tank 6 is sent to the nozzle 4 by the pump 5, and the water is sprayed to the heat radiating portion 2 of the condenser by the nozzle 4. In this method, the water sprayed to the heat radiating section 2 evaporates in the heat radiating section, and the latent heat at the time of evaporation is removed from the heat radiating section, whereby the refrigerant in the condenser body is cooled. This evaporation occurs at a constant temperature and is mixed with the air sent from the blower 3 between the nozzle 4 and the heat radiating portion 2, and has an effect of lowering the temperature of the air by evaporation at that portion. It is also effective in lowering the temperature. Furthermore, since the heat transfer coefficient by evaporation is much larger than that of air, the cooling effect of the refrigerant in the condenser is high.

However, the spray of water compensates for the shortage of heat exchange with air in the radiator, and if an excess amount of water is supplied that is more than the amount of heat required for liquefaction of the refrigerant, water that cannot be evaporated will radiate heat. It remains on the surface of the part and causes an action of inhibiting heat exchange due to the formation of a thick liquid film. Therefore, in the present invention, the supply of water by the pump 5 is stopped once after spraying a predetermined amount of water using the timer 7, and the water is constantly evaporated so that the sprayed water evaporates and water is sprayed again at the same time. It is characterized in that the water is smoothly evaporated by performing it at a time interval that can be maintained. Thereby, the heat transfer from the heat radiating portion is performed in the best condition.

In addition, since the water used for evaporation is sealed in the water storage tank 6, a cleaning agent for preventing substances such as alcohol and the like which are easy to evaporate and heat transfer and dirt and rust due to spraying of water as described above. Rust preventives and the like can be added for use.

In FIG. 1, the water in the water storage tank 6 is sprayed by being pressurized by the pump 5, but when the pump cannot be used, the water in the water storage tank 6 is separately pressurized by using an air compressor, and the water is sprayed by the pressure. There is also a way to do it. In that case, the pump 5 is not required, but water can be sprayed at appropriate intervals by providing an electromagnetic valve or the like in the water pipe. Furthermore, it is also possible to use a static pressure of the flow of air for pressurizing the fluid, entrain water with air, and use the surface tension of the gravitational liquid, or a combination of these methods.

The optimal amount of spray varies depending on the operating conditions of the refrigerator,
In this case, it is effective to provide a detector such as a thermometer or a pressure gauge in the condenser, observe the operating conditions of the refrigerant in the condenser, and adjust the water spray interval accordingly. In this case, it is possible to use a method in which the signal obtained from the detector is converted into a start signal of the pump via the controller, and thereby the spraying interval is adjusted. Also in this case, when the pump is not used, an electromagnetic valve or the like is provided in the water supply system, whereby the spraying interval can be adjusted. Further, the detector can be attached to the evaporator side and can be detected at the cooling output side. Furthermore, as a replenishment method, the amount of water consumed by evaporation can be used as a method of supplying water condensed in the evaporator with cooling of the air to a tank.

There is also a method of installing a refrigerator mounted on a mobile device or a tank if continuous water supply is not possible, and replenishing water in the tank as necessary. When the supply can be sufficiently performed, water can be constantly supplied by using the apparatus together with a water supply device, which is effective in reducing the size of the condenser and improving the refrigerating capacity.

These methods are intended for external heat radiation in the condenser of the refrigerator, but also when the medium to be cooled is a medium that does not accompany condensation and is cooled using air,
This is effective as a method for improving the cooling capacity. The optimum value of the amount of water sprayed in this cooling is preferably slightly lower than the value at which air is saturated by evaporation of water.

Application Example 1 An experiment for improving the cooling capacity was performed using an existing cooling device mounted on a vehicle. The cooling device used had a design capacity of 3,300 kcal / hr, and was provided with a cooling capacity improving mechanism as shown in 4 to 7 in FIG. Two nozzles made of plastic with a spray rate of 25 cc / min are used, connected to a pump with a maximum flow rate of 50 cc / min operated by a 12 VDC power supply of a car and a plastic tank with a capacity of 5, and in front of the nozzle. A filter was provided to prevent nozzle clogging. As for the spray interval, water was sprayed for 1 second, stopped for 2 seconds to evaporate the water, and this was continuously repeated by a timer.

FIG. 2 is a graph showing experimental results of the above apparatus. When the operation of the compression refrigerator started when the indoor air temperature was 40 ° C and the outside air temperature was 40 ° C, the room temperature dropped to 28 ° C and the cooling output was 2,100 kcal / hr. However, since the outside air temperature is high, it is not possible to generate any more cooling output. Next, when water is sprayed intermittently from the nozzle to the radiator of the condenser of the refrigerator according to the above method, air at 8 ° C. is obtained at the evaporator portion of the refrigerator, and the indoor air temperature drops to 15 ° C. It became clear. The cooling output at this time is 3,400k
At cal / hr, the water consumption per hour was 1,000 cc. In addition, the chain line is an example in the case of not spraying water.

Application Example 2 Water was sprayed in the same manner as in Application Example 1, and an experiment for improving the cooling performance was performed. However, the spraying of water was performed by detecting the outlet temperature of the radiating air from the condenser and responding to the temperature condition. Then, the method of spraying water by operating the pump 4 of FIG. 1 was implemented. The spray method, amount and interval are the same as those in the first embodiment. As a control standard, water was sprayed when the outlet temperature of the radiating air became 40 ° C or higher, and when the outlet temperature of the radiating air became 40 ° C or lower, only the air was released. As a result, it became clear that a room air temperature of 20 ° C. or less could be ensured in a steady state, and the water consumption was 500 cc.

Effect of the Invention According to the method of the present invention, the condensation of the cooling medium in the condenser is significantly reduced by a very simple operation of entraining a small amount of water into the air in the form of fine droplets and supplying the air to the radiator of the condenser. Since it can be promoted, it can be suitably used for refrigerators used in mobile bodies such as automobiles and trains. In addition, there is no need to increase the size of the heat radiating section and the blower as in the related art, so that there is an advantage that the entire refrigerator can be reduced in size.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one example of the method of the present invention, and FIG. 2 is a graph showing a state in which the temperature inside the condenser changes with time according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Condenser, 2 ... Radiator 3 ... Blower 4, ... Nozzle 5 ... Pump, 6 ... Water storage tank 7 ... Timer, 8 ... Expansion valve 9 ... Evaporator

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-250296 (JP, A) JP-A-55-105162 (JP, A) Fully open Showa 61-165213 (JP, U) Really open Showa 56- 149869 (JP, U) Shokai Sho 62-148412 (JP, U) Shokai Sho 55-108366 (JP, U) "Heat Exchanger Handbook"

Claims (5)

(57) [Claims] When operating the air-cooled condenser of a refrigerator having a radiator, when the temperature in the condenser reaches the liquefaction limit temperature of the refrigerant, no liquid film is formed on the surface of the radiator. And by supplying an amount of water that can evaporate in 0.1 to 2 seconds as fine droplets with the air, thereby utilizing the latent heat of evaporation of water and the sensible heat of the air to reduce the temperature in the condenser. A method for accelerating condensation of a cooling medium, comprising: performing a process of lowering the temperature to a temperature equal to or lower than a liquefaction temperature; 2. The method according to claim 1, wherein the supplied water is a heat transfer promoter, an evaporation promoter,
The method according to claim 1, further comprising at least one additive selected from a detergent and a rust inhibitor. 3. The method according to claim 1, wherein the supply amount of water is controlled according to a change in the output of the refrigerator or the operating temperature condition. 4. The method according to claim 1, wherein the water is supplied to the heat radiating portion by using a static pressure of an air flow for pressurizing the water to entrain the water. 5. A method according to claim 1, wherein part or all of the condensed water generated by cooling the refrigerator is reused as water to be supplied.
The method according to any of the above.