Last Updated on November 1, 2021 by Shawn Lee
IV. Design Points of Groundwater Heat Exchange System
1. The design procedure of groundwater heat exchange system is as follows:
- Determine the total amount of underground water required for this project;
- Selection and design of groundwater recharge methods;
- Determine the number and location of heat source wells (pumping wells and reinjection wells);
- Design of heat source wells; Low well or well group pipeline design; Selection and calculation of plate heat exchanger:
- Selection and arrangement of wells, pumps and other equipment.
2.Types and application scope of heat source wells.
Heat source well is the general name of pumping well and recharge well of groundwater heat pump air conditioning system, which is a groundwater heat exchange system
An important part of. Its function is to take out qualified groundwater from underground aquifer and send it to heat exchanger Set or send directly to the water source heat pump for heat exchange; And then return to the aquifer through the recharge well.
3.Structure of tube well
- Tube wells are mainly composed of well chambers, casing pipes, filters, settling pipes, etc. The diameter of existing tube wells in China is 200mm, 300mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm and other specifications.
- Well chamber. Its function is to install well pump motor, wellhead valve, pressure gauge, etc., to protect the wellhead from pollution and provide a place for operation, management and maintenance. Low casing pipe. It is installed in rock and soil sections (such as clay sections, etc.) where water is not needed, and its function is to reinforce the shaft lining and isolate the aquifer with poor water quality. Low filter (also known as flower tube). It is a pipe with holes or gaps which is directly connected with the casing pipe and installed in the aquifer. Its function is to draw groundwater and block sand grains from the aquifer from entering the well.
- sedimentation pipe. It is located at the bottom of the tube well, and is used for settling fine sediment particles into the well and sediment precipitated from groundwater. The length of the settling pipe depends on the depth of the well and the possibility of settling sand in the well water, generally 2~10m
4.Filter of heat source tube well
There are many types of filters, which can be divided into gravel-filled and non-gravel-filled. Gravel layers of certain specifications are backfilled around the filters to form gravel-filled filters. Otherwise, the filter is directly lowered to the aquifer part of the well, that is, the gravel-free filter. Commonly used filter types are: steel skeleton wire wrapping, steel pipe seam wire wrapping, steel pipe perforation, steel pipe perforation wire wrapping, steel pipe perforation gravel sticking, double-layer gravel filling filter, etc. The selection principles are as follows:
- gravel filter should be selected in all kinds of sand, gravel and pebble aquifers to prevent sand gushing and maintain the stability of aquifers;
- Under the condition of ensuring the strength requirements, filters with larger porosity should be adopted as far as possible;
- In areas with fine sand and high iron content, double-layer gravel filter should be adopted for heat source wells alternately used for pumping and recharging.
V. Key points of underground water pipe system design
The groundwater system should adopt variable flow design, and the groundwater supply pipe should be insulated;
Outdoor pipelines should be laid underground. The buried depth shall be determined according to local soil freezing line, external load, pipe performance, anti-floating requirements, crossing with other pipelines and other factors.
Groundwater supply pipes and recharge shall not be connected with municipal pipelines.
VI.Several problems should be paid attention to in the desig
- if the water quality of well water is not suitable for the use requirements of well water source heat pump cold and hot water units, corresponding technical measures can be taken (such as adding desander, sedimentation tank, water purification filter, electronic water treatment instrument, iron removal equipment, etc.) to treat the water quality to meet the requirements of the units; Or adopt an indirect water supply system with a plate heat exchanger to separate well water from the unit. Completely avoid the possible corrosion of well water to units.
- Water is one of the important earth resources. Therefore, in order to protect groundwater resources in design and use, measures of recharge must be taken. The effective recharge of well water can keep the aquifer head pressure and prevent the ground from sinking. It can also supplement the groundwater source, adjust the groundwater level and maintain the quantity balance. In the process of well water recharge, we should pay attention to the quality of recharge water and prevent recharge After that, it will cause regional groundwater pollution.
- In order to prevent and deal with the blockage of tube wells, measures should be taken to ensure the normal operation of reinjection wells.
- With the use of time, the capacity of production wells and recharge wells will decrease, and even their capacity can no longer meet the needs of heat pump operation. This process can be summarized by the concept of well aging. To prevent rapid aging of wells. The following technical measures should be taken: Iron components must be embalmed;
- The length and effective filtering area of the filter pipe of the reinjection well shall be at least 3~5 times that of the pumping pipe;
● Recharge wells should be equipped with at least 1m water collecting pipes; Each well must be provided with a well nest with a diameter of about 1m and a depth of about 1.3m, which is used for installing wellhead devices.
- The filter pipes of production wells and recharge wells must be deeply buried underground. Even if the groundwater level drops seriously, the upper edge of the filter pipe should not be exposed to the water surface;