Ground source heat pump working principle, classification and application

Heat pump works

As a natural phenomenon, just as water flows from low to high, the heat also always flows from high to low temperature. But people can create machines that use water pumps to pump heat from low to high temperatures, just as water is raised from low to high. Therefore, the heat pump is essentially a heat lifting device, which itself consumes a part of the energy, excavates the stored energy in the environmental medium and increases the use of the temperature. The heat pump consumes only a third of the heat One or lower, which is also the energy-saving features of the heat pump.

The principle of heat pump and refrigeration system components and functions are the same, the vapor compression heat pump (refrigeration) system consists of compressor, evaporator, condenser and throttle valve:

The compressor plays the role of compressing and conveying the circulating refrigerant from low temperature to high temperature and high pressure and is the heart of the heat pump (refrigeration) system.

Evaporator is the output of cold equipment, its role is to flow through the throttle valve refrigerant liquid evaporation to absorb the heat of the object being cooled, to achieve the purpose of refrigeration;

Condenser is the output of heat equipment, heat absorbed from the evaporator along with the compressor work of the heat converted by the cooling medium in the condenser away, to achieve the purpose of heating;

Expansion valve or throttle on the working fluid play a role in throttling and depressurization, and regulate the flow of refrigerant into the evaporator cycle.

According to the second law of thermodynamics, the power consumed by the compressor (electric energy) plays a compensating role, so that the circulating working fluid continuously absorbs heat from the low-temperature environment and radiates heat to the high-temperature environment and cycles cyclically.

Heat pump classification

Heat pump is the need for the heat of the condenser, the evaporator heat from the environment, this time from the environment to heat the object is called the heat; the opposite is the need to cool the evaporator, the condenser heat to the environment, this time The object of environmental heat release is called cold source.

Evaporator condenser according to the circulating refrigerant and the environment of the heat transfer medium is divided into two main forms of air heat exchange and water heat exchange. This heat pump or refrigerator according to the environment and the heat transfer medium can be divided into water - water, water - air, air - water, and air - air four categories.

The use of air as a heat source heat pump, called the air source heat pump. Air source heat pump has a long history, and its installation and use are very convenient, widely used. However, due to the difference of regional air temperature, the typical application in our country is south of the Yangtze River. In North China, the mean temperature in winter is below zero degrees Celsius. Air source heat pumps are not only run in poor conditions and have poor stability, but also are inefficient because of frost formation.

The use of water as a heat source heat pump, called water source heat pump. Water is an excellent heat source. Its heat capacity is large and its heat transfer performance is good. Generally, the efficiency and capacity of cooling and heating of water source heat pump are higher than that of air source heat pump. However, the application of water source heat pump is much less than that of air source heat pump due to the limitation of water source.

Ground source heat pump working principle and classification

Ground source heat pump is a form of water source heat pump, it is the use of water and ground energy (groundwater, soil or surface water) for cold and heat exchange as a source of heat and cold water source heat pump in winter to heat "Come out to supply indoor heating, at this time can be a" heat source "; summer to remove indoor heat, released into the groundwater, soil or surface water, at this time can be" cold source. "

Ground source heat pump heating air conditioning system is divided into three parts: outdoor heat exchange system, water source heat pump units and indoor heating air conditioning terminal system.

Water source heat pump which there are two main forms: water - water or water - air type. Heat transfer between the three systems * water or air heat exchange medium, heat exchange medium between water source heat pump and ground energy is water, and heat exchange medium of building heating and air conditioning end can be water or air.

Compared with air source heat pump ground source heat pump, there are many advantages: (1) small temperature fluctuations throughout the year. Winter temperature is higher than the air temperature, summer air temperature is lower than the ground, so the ground source heat pump heating, cooling factor is higher than the air source heat pump, generally higher than 40%, so energy saving and cost savings of about 40%. (2) Winter operation does not require defrosting, reducing frost and defrosting losses. (3) ground source has a better energy storage effect.

Ground source classification

Ground source in accordance with the different ways of outdoor heat exchange can be divided into three categories:

1. Soil Buried Coil System, 2. Groundwater System, 3. Surface Water System.

According to whether the circulating water is a closed system, the ground can be divided into closed-loop and open-loop system.

Closed-loop system

Such as buried coil method (vertical or horizontal buried pipe), surface water to place the heat exchanger.

Open-loop systems such as pumping groundwater or surface water.

In addition, there is a "direct expansion" that does not use intermediate water to transfer heat as the system described above. Instead, a heat exchanger (evaporator) of the heat pump is directly buried for heat exchange.

Ground source heat pump application

Ground source heat pump Applications from the application of building objects can be divided into two major categories of domestic and commercial, from the transport of cold and heat can be divided into centralized systems, decentralized systems and hybrid systems.

Household systems

Users use their own heat pump, ground and water or duct delivery system for hot and cold supply, and more for small houses, villas and other household air-conditioning.

Centralized system

Heat pump is arranged in the engine room, hot and cold concentrated through the air duct or water distribution system to each room.

Disperse the system

With the central pump, using the water loop way to send water to the user as a cold source of heat, the user individually use their own heat pump unit to regulate the air. Generally used in office buildings, schools, commercial buildings, etc., this system can be fully used in the user's cold and heat on the electricity, easy to measure, suitable for the current independent heat measurement requirements.

Mixed system

A system that uses a combination of ground sources and cooling towers or boilers as a source of heat and cooling, the hybrid system is very similar to a decentralized system except that cooling towers or boilers are added to the cold or hot source system.

In the south, the cooling load is large and the heat load is low. It is suitable for the combined use of ground source and cooling tower in summer and only the ground source in winter. In the north, the heat load is large and the cooling load is low. In winter, it is suitable for the combined use of ground sources and boilers. In summer, only the ground source is used. This will reduce the capacity and size of the ground source and save on investment.

Dispersing systems or hybrid systems are essentially water ring heat pump air conditioning systems.


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