More than 600 cities in China with more than 400 lack of water. Due to the direct use of property of water water central air conditioning water system is very large, this is many areas can't meet. And, in fact, does not ensure that no pollution to groundwater 100% to return to the underground. So, in most parts of our country is not suitable for use direct use of groundwater water source heat pump central air-conditioning system. Buried pipe water central air conditioning is not restricted by water. The water shortage in our country the basic countries qian. Buried pipe water central air conditioning system is divided into vertical buried tube type and horizontal buried pipe type two kinds.

2.2.2.1 vertical buried tube type

The depth of the vertical buried tube in dozens of meters, even deeper. In order to ensure that the fluctuation of water cycle, the underground vertical buried pipe, generally USES the u tube, water by "' end of the pipe into the u tube, the u tube flow back to the ' 'end, in the process of flow and soil heat transfer outside tube, as shown in figure 2, l (e). In order to prevent frostbite, buried pipe flow generally not water, but the ethylene glycol solution. Heating, heat, water source heat pump units to absorb ethylene glycol

To the end of the indoor equipment, for heating; To the water source heat pump units provide heat source is vertical buried tube b two yeast solution, ethylene glycol solution after entering water source heat pump units, after the release of heat temperature is reduced, then flow back to the vertical cut pipe and the soil outside the buried tube heat exchange, temperature, and then enter the water source heat pump units, water source heat pump heating. Cooling process is just the opposite.

Due to the vertical buried tube tube and drill for drilling rig, drilling fL expenses is larger. So, for the factory to improve heat transfer capacity of single well, reduce drilling costs, sometimes in a look well at the same time two groups of tJ coil. Before the buried pipe to drilling sampling, the same record of geological structure. For the different geological structure, buried pipe of the rate of heat transfer, heat transfer capacity influence is very big. For storage quantity of heat, heat transfer coefficient of the land quality construction, to reduce the distance between the buried tube well, the in - 'eyes and therefore cannot be buried u-tube in both groups, otherwise will affect normal operation of the system, and it's need to increase the number of drilling, thus increasing buried pipe area.

2.2.2.2 horizontal buried pipe

Horizontal buried pipe construction simple, under the pipe can be buried under the flower beds, lawns, roads, had no effect on the ground attachments, as shown in figure 2-1 (6).

Horizontal buried pipe covers an area of big, only applicable to villa and locally by the small central air conditioning system of air conditioning. In cold northern adopts horizontal buried pipe, the pipe must be at least in the frozen lu: layer l m here, so on shi will cost far more than the vertical buried tube type, so it is not suitable for use in cold area.

F buried pipe system as heat and cold source, water source heat pump central air-conditioning system in the practical application has the problem of temperature fluctuation is bigger. Is determined, the number of buried pipes in use cannot adjust, basic fixed heat transfer coefficient of the system. When heating, because of the heat transfer coefficient of buried pipe system is constant, the heat load of the system is constantly changing, system heat load increases, the buried tube heat transfer temperature difference between inside and outside will be increased.

From 10 buried pipe is large, the cost of other in design 1 when the number of buried pipes is not possible to do very big, but as much as possible the use of soil heat storage, 'like to use below the freezing point. Because the system constantly absorbing the heat inside the soil, with the increase of time, F soil temperature will be falling, the ethylene glycol solution tube temperature it is only natural that drops. The water source heat pump units of the heating capacity increased with the increase of time. The temperature of the horizontal buried pipe system passive is more serious.