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 kind of 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.

(A) 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 in the condenser liquefaction heat, heat pump cycle, so that the heat can be continuously exchanged, and through the valve switch to make the unit Realize the conversion of heating and cooling functions.

Natural gas heat pump equipment is divided into:

1) Unit system, including gas engines, compressors, condensers, evaporators, expansion valves, etc .; 2) Heat recovery system including cylinder liner hydrothermal recovery heat exchanger, exhaust heat recovery heat exchanger and hot water tank ;

3) gas supply and exhaust system;

4) cold water system, including cooling pumps, chilled water pumps, cooling towers and so on. 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 heat quantity 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 diagram shown in Figure 1 below:

(1) cooling operation mode

â‘  gas engine-driven compressor, compressed refrigerant (refrigerant).

â‘¡ compressed high temperature and pressure refrigerant in the condenser cooling, condensing heat and liquefied release.

â‘¢ liquefied refrigerant, the expansion valve into the evaporator, vaporization from the indoor air to absorb the heat required for evaporation, at the same time

Make indoor air cool, ie cool. '

â‘£ The evaporated refrigerant returns to the compressor and is compressed again. '

⑤ gas engine exhaust heat (cylinder heat and high temperature flue gas) as hot water recycling use.

(2) Heating operation mode

â‘  gas engine-driven compressor, compressed refrigerant (refrigerant).

â‘¡ 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.

â‘¢ liquefied refrigerant, the expansion valve into the evaporator, vaporization from the outdoor air to absorb the heat required for evaporation.

â‘£ The evaporated refrigerant returns to the compressor and is compressed again.

⑤ gas engine heat recovery as hot water use.

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