0 Introduction "Exergy", as a parameter that evaluates the value of energy, regulates the "value" of energy from both "quantity" and "quality" and solves the problem that there is no single parameter in thermodynamics that can evaluate energy separately The question of value has changed people's traditional viewpoints on the nature of energy, the loss of energy and the conversion efficiency that can be achieved, providing the scientific basis for thermal analysis. At the same time, it also profoundly reveals the essence of deterioration and degeneration of energy in the process of conversion, indicating the direction for rational use of energy. The function of a heat pump is to draw heat from the environment and pass it on to a heated object (a hot object). At present, foreign heat pump technology has been widely used, and is still growing. With the national emphasis on energy conservation and environmental protection, the development and promotion of heat pumps in our country have also been rapidly developed. In our field of HVAC, heat pumps, especially compression heat pump has a very wide range of applications. In this paper, the exergy analysis is applied to the application of compression heat pump in heating system. Exergy and Energy For a long time, people were accustomed to measuring the value of energy from the amount of energy, regardless of what energy it consumed. As we all know, different forms of energy, the value of their power use is not the same. Even in the same form of energy, under different conditions also have different abilities. Although "enthalpy" and "internal energy" have the meaning and dimension of "energy", they do not reflect the quality of energy. However, "entropy" is closely related to the "quality" of energy, but it can not reflect the "quantity" of energy and there is no direct "quality" of energy. In order to be able to use it economically, it is necessary to adopt the same measure that reflects both the quantity and the "qualitative" differences between the various energies. Exergy is just such a thermodynamic physical quantity that scientifically evaluates the value of energy. 1.1 The concept of exergy and fire The energy of all forms is not the same as the ability to convert to advanced energy. If you use this conversion capacity as a yardstick, you can evaluate the pros and cons of various forms of energy. However, the size of the conversion capacity is related to the environmental conditions and is also related to the degree of irreversibility of the conversion process. Therefore, in fact, under the given environmental conditions, the theoretically maximum conversion capacity can be used as a measure of energy taste, which is called Exergy. It is defined as follows: When the system reversibly changes from an arbitrary state to a state that is in balance with a given environment, it can theoretically be infinitely converted into energy of any other form of energy, which is called exergy [1] . Since the most complete conversion is possible only in the reversible process, it can be assumed that (exergy) is the minimum useful work or theoretically minimum useful work theoretically done in a reversible process under given environmental conditions. Correspondingly, everything that can not be converted to exergy is called Anergy. Any energy E consists of two parts, Ex and A, ie E = Ex + An 1.2 Energy Conversion Rules From the viewpoints of exergy and fire, energy The conversion law can be summarized as follows: (1) (exergy) and (fire) the total amount of conservation, that is, we often say that the principle of conservation of energy. (2) (fire no) can no longer be converted to (exergy), otherwise it will violate the second law of thermodynamics. (3) reversible process does not appear devalued deterioration, so the (exergy) the total conservation. (4) In all practical irreversible processes, inevitable devaluations can occur. Exergy will be partially "degenerated" into "extinction" and become exergy losses. Because this kind of degradation can not be compensated, the exergy loss is the real loss in energy conversion. (5) The exergy value of isolated systems does not increase, but only decreases, at most, the same, that is, the exergy reduction principle of the isolated system. So (exergy), like entropy, can be used as a criterion for the natural process directionality. 1.3 Heat (Exergy) If the temperature of a system is higher than the ambient temperature, when the system reversibly changes from any state to a state that is in balance with the state of the environment (aka "dead state"), the heat Q is released, The outside world to make the greatest usefulness. This maximum useful work is called ExQ heat. If the heat Q is obtained from a constant temperature heat source at a thermodynamic temperature T and the ambient temperature is T0, the maximum work Wmax that may be obtained from the heat, that is, ExQ is ExQ = Wmax == Q Exergy has the following Nature: (1) Heat (exergy) is the maximum useful energy that can be converted in the heat released by the system. (2) The amount of heat (exergy) is not only related to the size of Q, but also to the system temperature T and the ambient temperature T0. (3) The same quantity of Q, with different heat (exergy) at different temperatures T, the higher the T is, the greater the exergy is when the ambient temperature is determined. (4) Heat (exergy) is the same amount of process as heat, not state quantity. Exergy balance and exergy analysis When we analyze the energy of a thermal system, we hope to find out the parts and causes of the loss through the analysis of the process of energy morphological changes, the quantitative calculation of the effective use of energy and the loss In order to propose improvements and forecast the improved results. We usually use the energy balance analysis is divided into heat balance (enthalpy balance) analysis and (exergy) balance analysis of two. 2.1 (Exergy) balance and (exergy) loss of energy conservation is a common law, the energy balance of payments should be maintained. However, exergy is only an available part of energy, and its income and expenditure are generally unbalanced. During the actual conversion process, some of the available energy can be converted into unusable energy and the exergy will be reduced, which is called Exergy loss. This does not violate the law of conservation of energy. Exergy balance is the sum of (exergy) and exergy loss (unavailability energy). Supposing that the input exergy across the system boundary is Exin, the exergy output is Exout, the system exergy loss is Ii and the external work is W, then their equilibrium relationship is ΣExin + W = Σ Exout + ΣIi (Exergy) balance not only considers the amount of energy, but also take into account the quality of energy. In considering the exergy balance, the key is the need to write down the exergy losses in order to maintain balance. Among them, the internal irreversible (exergy) loss term is not reflected in the heat balance. Therefore, there is a qualitative difference between the two methods of analysis. However, there is an intrinsic link between the two and the exergy balance is based on heat balance. 2.2 Exergy Analysis and Exergy Efficiency The usual caloric balance and energy conversion efficiency do not reflect the degree of exergy utilization, so we introduced the concept of exergy efficiency. Exergy efficiency and energy conversion efficiency are defined similarly, except that exergy efficiency is the ratio of earnings (exergy) to payments (exergy). (Exergy) efficiency Ex With exergy efficiency concepts, we can set up an exergy balance for a given thermal system and perform an exergy analysis of it to achieve the following: 1) Quantitative calculation of energy (exergy) of the various expenditures, utilization and loss situation. Revenue and expenditure balance is the basis, the flow of energy to include revenue items and a variety of loss items, according to the proportion of the distribution can be divided primary and secondary. (2) Through the calculation of efficiency, to determine the effect of energy conversion and the degree of effective use. (3) Analyze the rationality of energy utilization, analyze various loss size and influencing factors, propose the possibility of improvement and ways to improve, and predict the improved energy-saving effect. 3 Exergy Analysis of a Compression Heat Pump A "heat pump" is an energy utilization device that transfers heat from a heating object to a hot object. Proper use of heat pumps can turn those heating heat that can not be directly used into useful heat, thereby increasing heat utilization and saving a lot of fuel. Not only that, with the help of heat pumps, it is also possible to harness the inexhaustible low-heat sources of the atmosphere, oceans, rivers and earth. Although the heat pump itself is not a natural energy source, it does indeed have an "energy" effect from the point of view of the energy it can output. So it is called "special energy source" [2]. 3.1 compression heat pump works Heat pump works the same as the cooling device, but also the use of reverse cycle. However, the purpose is not to cool but to heat, that is, the range of working temperature is different from that of a refrigerator. It has two types: compression and absorption. The following brief introduction to the working principle of compression heat pump. Compression heat pumps heat at the cost of consuming a portion of high energy (mechanical or electrical energy), as shown in Figure 3-1. Low-boiling point refrigerant through the compressor, the external power consumption W, the working fluid pressure and temperature. Due to its temperature above the temperature required for heating TH, let it through the condenser to the indoor heat supply Q1 itself is condensed. Then through the expansion valve throttling pressure, while the temperature is also reduced. Since its temperature will be lower than the temperature TL of the heat source (usually the ambient temperature T0), the heat is absorbed by the evaporator Q2 and evaporates. Vapor back to the compressor to continue to compress, to complete a cycle. Figure 3-1 Compressible heat pump system 1 Compressor 2 Condenser 3 Expansion valve 4 Evaporator As can be seen from the above equation, if (T1-T2) is smaller, or T2 / T1 is larger The bigger Always greater than 1. When T2 / T1 approaches 1, it tends to infinity. This shows that the amount of heat that the heat pump can provide is in excess of the work consumed. And, the smaller the difference in heat transfer temperature, the greater its effectiveness. In this regard, the use of heat pump heating is the most suitable. In addition to the actual heat pump heat transfer irreversible loss, due to the compressor and the expansion valve there is also an irreversible loss, so the actual heating coefficient will be less than the theoretical value, that is, in determining the heat pump heat, heat cycle parameters and Compressor efficiency, you can use the refrigerant thermodynamic properties of the chart to calculate the actual value of the heat coefficient = type - heat pump effective coefficient. Exergy Analysis of Compressible Heat Pump The exergy analysis of the heat pump is shown in Figure 3-3. The shaded area in the figure represents the exergy stream and the rest is ((firefree)) stream. If the cold source temperature TL is higher than the ambient temperature T0, then the heat pump Q2 contains a small amount of exergy, its exergy value is ExQ, L = Q2 = (Q1-W) Indoor heat Q1 has ExQ, H = Q1 In Figure 3-3, A is the sum of the exergy losses in the heat pump. B for the refrigerant to the indoor heat transfer, the temperature difference