Both refrigeration units and heat pump units are inverse Carnot cycles, but the efficiency of the reverse Carnot cycle is determined by the temperature difference between the high-temperature condenser and the low-temperature evaporator. Based on the idea of conservation of heat energy and the principle that a perpetual motion machine is impossible, Carnot further proved that the efficiency of all actual heat engines working between a high-temperature heat source at the same temperature and a low-temperature heat source at the same temperature will not be greater than that of a reversible Carnot heat engine working between the same heat sources. Carnot deduced from this that the efficiency of an ideal reversible Carnot heat engine has a maximum, which is determined only by the temperature of the heater and condenser, and that the efficiency of all actual heat engines is lower than this extreme.
When the Carnot cycle process runs in a clockwise direction, the system does work externally, and its a 0, while the q=a 0 system is an endothermic process. When the Carnot cycle process runs in a counterclockwise direction, then it is the outside world that does work on the system, its a 0, when q = a 0 the system is an exothermic process. The system uses heat energy to do external work, which is a positive Carnot cycle, and its efficiency is =a q=(q1-q2) q1=1-q2 q1. The refrigeration efficiency (coefficient) of the reverse Carnot cycle is =q2 a=q2(q1-q2), because q1 q2=t1 t2, then =t2 (t1-t2)=1 -1 , the value interval is 0, it can be seen that the lower the temperature of the low-temperature heat source, the greater the temperature difference, the smaller the refrigeration coefficient, and the greater the refrigeration efficiency. It can be seen that the refrigeration coefficient or heat pump efficiency is determined by the temperature difference between the condenser and the evaporator.
In the case of extremely cold weather, the heat pump operation is difficult to stabilize, and its energy efficiency ratio is also very low, in order to cope with the heating in extremely cold weather, the use of overlay technology scheme and two-stage compression or gas enthalpy increase technology method to solve the problem of insufficient heating temperature, and will produce new problems, this new problem is that it is very difficult to adjust the heating load change, there will be more than 70% of the time of low-load operation in winter, and the control of low-load operation is generally achieved by using frequency conversion technology. However, the stacked heat pump and the two-stage compression heat pump must be operated by two compressors at the same time to maintain normal operation, even if the frequency conversion technology is used, the control range is minimal, and the two-stage compression heat pump technology will be even more so. When the heat pump is operating at about 75% of its rated power, its energy efficiency ratio is the highest, and if it is below 50%, its energy efficiency ratio will drop sharply. Recently, some relevant scientific and technological workers have invented and innovated the cascade heat pump unit that can realize the operation of a single compressor under low load, but its process structure is complex, which increases the user's investment cost, and the failure during operation also increases accordingly, so it is not favored by the user, and its market promotion is also difficult.
In order to solve the above problems, the mutual aid dual-cycle heat pump technology was invented, which can not only solve the problem of insufficient heating temperature in extremely cold weather, but also solve the problem of difficult operation of refrigeration and air conditioning in extremely high temperature weather, and can also adapt to the adjustment of a wider range of loads, and the frequency conversion of a single compressor can also achieve good operation. There is a greater point of interest is that its operating energy efficiency ratio is not comparable with all the current heat pump technology, in all the large temperature difference segmentation technology scheme, its large temperature difference segmentation it is the most perfect, is not to improve the temperature difference between the evaporator and the condenser of the unit, can realize the advantages of large temperature difference of the medium and the outside air heat exchange, is the current two-stage compression or overlay scheme can not be realized. The mutual aid dual-cycle heat pump adopts the principle of thermal feedback to achieve the heat amplification effect, which greatly improves the energy efficiency ratio of the unit. The so-called large temperature difference heat exchange advantage is based on the principle that temperature difference is the only power for heat exchange, to achieve the advantages of large temperature difference between the system medium and the outside air, if the efficient circulation of heat exchange inside the system is not the final result of heat exchange with the outside air large temperature difference, because the ultimate purpose of the heat exchange circulation system is to discharge the internal heat of the system or bring the heat of the outside air in, and the large temperature difference between the outside air and the heat exchange is equal to the high efficiency is undoubted, but it must be based on the fact that the temperature difference between the evaporator and the condenser remains relatively unchanged, so that the large temperature difference is considered an advantageIf the temperature difference between the evaporator and the condenser is large, it will inevitably consume more output power of the compressor.
Mutual aid dual-cycle heat pump is a circulation system that can exchange heat with the outside air by two independent refrigerant circulation systems, one group of refrigerant circulation is the main circulation system, and the other group of refrigerant circulation is the auxiliary circulation system, the main circulation system is the system facing the user's target, the auxiliary circulation system is a system facing the input of external air heat or heat exhaust to the outside air, and the main circulation system and the external air heat exchange working fluid circulation system can be closely linked through heat exchange, and the main circulation system and the auxiliary circulation system adopt mutual assistance to realize the transfer of heatWhether it is heat pump cycle or refrigeration cycle, the goal we pursue is to consume as little input electrical energy as possible, and at the same time to obtain more heat energy from the air, or discharge more heat from the outside air, and the technical method is to rely on more air flow to obtain more heat or discharge more heatOr lower the temperature of the air heat source to get more latent heat of water vapor?Or increase the temperature difference of the heat discharged from the system?This is definitely not a random choice that can maximize the efficiency of the system, it must follow the laws of thermodynamics and the inverse Carnot cycle principle to weigh the pros and cons. We must also consider the utilization value of water vapor latent heat in the air, the heat exchange medium is lower than air 5 and less than 10 heat exchange difference is definitely not a simple double heat relationship, because the temperature difference of reducing the air by 5 may not necessarily have water vapor latent heat released, if it is not reduced to the ** temperature corresponding to its relative humidity, there can be no condensate or frost layer below, even if the latent heat of water vapor can be obtained, its heat is very little;We know that the heat released by two equal volumes of air with different relative humidity with the same cooling amplitude will differ by hundreds of times, or even a thousand times, and this assumption is that the relative humidity is greater than 50%, and when the cooling amplitude exceeds 10, there will be dozens or hundreds of times of heat difference. Obviously, the air energy advantage obtained by a large temperature difference is many times greater than that of a small temperature difference at the same air flow. Although a small temperature difference and a large flow rate can reduce the compression ratio of the compressor to reduce the output power of the compressor, it will increase the motor power of the circulating pump and axial fan, and the volume of the heat exchanger equipment will also increase many times. In order to make the efficient operation of the thermal circulation system, in the end, it is to seek that the system can carry out efficient heat exchange with the outside air, and the efficient heat exchange means that the heat exchange between the large temperature difference and the outside air is the prerequisite, and the key is how to achieve the prerequisite of the large temperature difference. It is not advisable to use excessive power consumption to obtain a large temperature difference with the outside air, and the current heat pump steam production principle is realized in this way. Specifically, the compressor can not be formed into an excessively high compression ratio, only in this case to achieve a large temperature difference between the system medium and the outside air heat exchange is the best technical method. How to do this, this is the key technical content of this article. It is necessary to form the advantage of heat exchange with the large temperature difference of the outside air, and at the same time to reduce the temperature difference between the evaporator and the condenser to promote the compression ratio of the compressor to reduce, which is a good technical scheme that can be achieved at the same time. The mutual aid double-cycle heat pump system is to provide secondary heating conditions for the heat source of the main cycle with the help of auxiliary circulation, and at the same time can promote the temperature of the heat source of the auxiliary circulation heat pump to be improved, thereby reducing the compression ratio of the main circulation compressor, it is to transfer the low-temperature heat of the shared heat exchange medium fluid from the evaporator of the main circulation system through the auxiliary circulation heat pump system and feedback to the solution in the process of the main circulation evaporator, which is the technical method of the secondary heating heat source, and at the same time, the temperature of the shared heat exchange medium fluid can also be lowered lower, so as to facilitate the use of large temperature difference to obtain more water vapor latent heat heat from the outside air。 The cascade heat pump can only increase the heat source temperature of the secondary circulation heat pump by the primary circulation heat pump, but the primary circulation heat pump is still facing the extremely cold weather of the outside air.
There is no need to increase the temperature difference between the evaporator and the condenser to obtain the advantage of heat exchange with the large temperature difference between the outside air, which is our ultimate goal, so that in the face of extremely cold weather to ensure that the energy efficiency of the unit is relatively high-level operation, and at the same time, it can better absorb the latent heat of water vapor in the outside air. Obviously, it is much more cost-effective to absorb the latent heat of water vapour than the sensible heat of air. We don't need larger heat exchange equipment, we don't need more air volume, the fluid circulation volume will also be reduced, and we don't need to consume more electrical energy, just reduce the temperature of the shared heat exchange medium fluid by 5 more, and you can get many times the heat**, but you must take into account that the compression ratio of the compressor can not be increased. Therefore, the mutual dual-cycle heat pump technology has the following eight advantages compared with the existing technology:
1. Without increasing the compression ratio of the compressor, it can obtain the advantage of heat exchange with the outside air with a large temperature difference;
2. It can realize the heat exchange with small flow and large temperature difference, so that the volume of the heat exchanger can be greatly reduced and the equipment investment cost can be saved
3. The small flow and large temperature difference heat exchange reduces the motor power of the circulating pump and axial fan by more than 40%.
4. The small flow can also reduce the wear of the fluid on the wall surface of the heat exchanger, thereby prolonging the service life of the heat exchanger equipment
5. It can realize the independent work of a single compressor without affecting the normal operation of the system, compared with the two-stage compression scheme and the overlay heat pump technology, it has the advantage of coping with load change regulation, and the adjustment ability of the system output power is very prominent when the load changes greatly
6. It can cope with the efficient and stable heating operation in extremely cold weather, and provide users with a high heating temperature demand
7. It is very suitable for ultra-low temperature refrigeration, which can be used to liquefy hydrogen, which can play a role in helping the vigorous development of hydrogen energy vehicles, which has many advantages over two-stage compression
8、 Higher temperature heat energy can be obtained for drying, and even the production of steam is more economical than the steam produced by burning fossil energy, used for the demand for steam in some enterprise processes, and mutual multi-cycle can also be used to meet the demand for higher temperature heat, perhaps in the near future, mutual multi-cycle technology can be used to obtain heat from the air, and then the heat will be converted into electrical energy will become a reality, and the process process for air energy storage can transfer the heat from the air potential energy to the phase change material, and then obtain higher temperature steam for power generation through mutual multi-cycle heat pump。.