Forms of air-conditioning systems commonly used in engineering-Part 2

3. Fan coil + fresh air conditioning system

2) Air treatment process of fan coil + fresh air conditioning system

The fresh air and the fan coil each supply air to the air-conditioned rooms. In this way, even if the fan coil unit stops operating, the fresh air will remain unchanged.

Fresh air is mixed at the outlet of the fan coiler (pressure out end). This method does not need to set up a special fresh air outlet, which is more favourable to the ceiling arrangement; when the fan coil unit is in operation, the fresh air is required to raise the pressure at that point.

The fresh air is mixed with the return air from the fan coil and then sent to the air-conditioned room. Comparing this method with the above two methods, the number of room air changes is slightly reduced; when the fan coil unit stops running, the amount of fresh air is reduced.

(3) Selection principles of fan coil units

Select the appropriate model according to the usage requirements and floor plan.

According to the results of cold and heat load calculation, select the appropriate unit specifications, generally according to the summer cold load selection of fan coiler units.

Based on the room cooling load, select the model according to the cooling capacity at mid-range, and calibrate whether the winter heating capacity can meet the room heating requirements.

Combined with the actual use of working conditions, the unit's cooling capacity and heating capacity under standard working conditions are corrected so that the actual cooling and heating capacity of the selected unit is close to or greater than the calculated cooling and heating capacity.

Note the value of residual pressure outside the unit.

Pay attention to the noise value of the unit, and choose muffling measures reasonably.

4. Water-loop heat pump air-conditioning systems

A water loop heat pump air conditioning system is a form of all-water air conditioning system.

Water loop heat pumps, also known as water-to-air heat pumps, use water as the heat-carrying medium. When cooling, the unit releases heat to the water in the loop to lower the air temperature; when heating, it obtains heat from the water to heat the air.

Working principle of water ring heat pump unit

When the water ring heat pump unit operates under refrigeration condition, the built-in compressor of the water ring heat pump unit compresses the low-pressure low-temperature refrigerant vapour into high-temperature refrigerant gas into the condenser, and the refrigerant condenses into high-pressure liquid through the cooling effect of water in the condenser, and then enters into the evaporator after the throttling and expansion of the throttle device (expansion valve) to cool down the air passing through the water ring heat pump unit.

When the water ring heat pump unit operates in the heating condition, the system of the unit is the same as that of the cooling condition, but the difference is that the condenser becomes the evaporator in the cooling condition through the switching of the four-way valve in the heating condition, while the evaporator becomes the condenser in the cooling condition. The unit absorbs heat from the water through the evaporator, and releases heat from the condenser to the air passing through the water ring heat pump unit to heat the air.

By Sammi