Feasibility Analysis of Natural Gas Heat Pumps in the South of China

Natural gas engine heat pump, which is used for refrigeration in the south, can not only meet the needs of the refrigeration market, but also can play the role of peak load-shifting and load balancing at the same time due to its complementary characteristics with electric power. A good solution to optimize the use of gas pipelines and power grid resources. First, natural gas heat pump technology and its advantages Heat pump is a low temperature heat source to improve the grade to provide high-temperature heat source equipment. As the name suggests, the natural gas heat pump uses natural gas as the engine fuel, drives the compressor through combustion, and recovers the heat of the engine liner water and flue gas to improve the primary energy utilization rate and the operating cost of the heat pump unit. (1) natural gas heat pump technology Natural gas heat pump by circulating the refrigerant repeatedly physical phase transition process, respectively, in the evaporator gasification heat absorption, or liquefaction in the condenser heat, heat pump cycle, the heat is constantly exchanged, And through the valve switch to make the unit to achieve heating and cooling function conversion. Natural gas heat pump equipment is mainly composed of: 1) unit system, including gas engines, compressors, condensers, evaporators, expansion valves; 2) heat recovery system, including cylinder heat recovery water heat exchanger, exhaust heat recovery Heat exchangers and hot water tanks, etc .; 3) gas supply and exhaust systems; 4) cold water systems, including cooling pumps, chilled water pumps, cooling towers and the like. If the heat recovered by the system is used for cooling, an absorption chiller is also included in the chiller section. The working principle of natural gas heat pump is the same as that of refrigerator. According to the reverse cycle of heat engine, follow the second law of thermodynamics: Q can be drawn from low-temperature heat source by consuming some high energy (heat P). The heat is transferred to the high-temperature heat source Q heat to achieve the purpose of air conditioning (heating or cooling). The amount of heat supplied is greater than the high energy (natural gas) consumed, which is the sum of the high energy and the low energy absorbed. With the formula: Q ^ = Q + P low temperature heat source can be air, well water, sea water, soil heat, solar energy and so on. Air source heat pump is the main type of natural gas heat pump, divided into "air / water" heat pump and "air / air" heat pump two types, the operating principle is shown in Figure 1 below: (1) cooling mode of operation ① gas engine driven compressor , Compressed working fluid (refrigerant). ② compressed high temperature and pressure refrigerant in the condenser cooling, condensing heat and liquefied release. ③ liquefied refrigerant, the expansion valve into the evaporator from the indoor air to absorb the heat required for evaporation, while allowing indoor air cooling, that is, refrigeration. '④ After evaporation of the refrigerant back to the compressor, was again compressed. '⑤ gas engine exhaust heat (cylinder liner heat and high temperature flue gas) as hot water recycling use. (2) heating mode of operation ① gas engine-driven compressor, compressed refrigerant (refrigerant). ② compressed high temperature and pressure refrigerant in the condenser cooling, condensing heat and liquefied release. Condensation heat used to heat the indoor air to achieve the heating effect, that is, heating. ③ liquefied refrigerant, the expansion valve into the evaporator, vaporization from the outdoor air to absorb the heat required for evaporation. ④ The evaporated refrigerant returns to the compressor and is compressed again. ⑤ gas engine heat recovery as hot water use.