How to choose the modular air handling unit ?
1. Several issues that should be paid attention to when choosing an air conditioner
When we select the modular air handling unit, we first determine the required air volume, air static pressure, heat and cooling, air outlet noise and air filtration requirements for the air conditioner according to the load calculation results of the air conditioner system. However, due to various reasons such as design or manufacturing, in use, we often find that the selected air-conditioning box has one or more problems, mainly including insufficient air cooling, insufficient cooling capacity, condensation on the outer surface of the cabinet, overflow of the condensate tray, and surface cooler Problems such as carrying water after the paragraph. Therefore, this requires us to strictly control the quality when selecting the equipment to prevent it from happening. My own experience is as follows:
(1) Box insulation
In order to prevent condensation on the outer shell of the cabinet, the national standard stipulates that the thermal resistance of the thermal insulation layer of the cabinet should not be less than 0.68m2 · K / W. At the same time, it should also prevent cold bridges generated at the junctions of various sections of the cabinet. Insulation materials are currently mostly made of PEF or polyurethane foam.
(2) Wind speed on the windward side
At present, in order to reduce the size of the product, some manufacturers often increase the wind speed of the windward side of the air conditioner box, which causes the consequences of water in the cold section of the air conditioner box; if the water baffle design is unreasonable, this problem is even more problematic. Seriously. Therefore, when selecting the model, we should control the wind speed on the windward side of the surface cooler at 2 ～ 2.5m / s.
(3) Air leakage index
The national standard stipulates that when the static pressure of the combined air conditioner is 700Pa, the air leakage rate within the machine shall not exceed 3%. In actual use, we found that the air leakage rate of the on-site air-conditioning box was as high as 10%. After analysis, this is mainly caused by the following reasons.
1) The performance of the sealing material is not good;
2) The structural design of the unit is unreasonable;
3) Poor quality of on-site installation;
4) The rigidity of the large air volume air conditioner box is poor, and it is easy to deform when starting and stopping operation.
(4) Insufficient cold and heat
The design and selection of surface coolers of domestic manufacturers are based on empirical formulas based on small sample test results. This itself has certain errors, and some companies copy the relevant samples from other manufacturers without the test conditions; Many domestic manufacturers are the main reason for the lack of cold and heat of such products. Therefore, we must personally understand their product testing methods when conducting field visits to manufacturers.
(5) Condensate tray overflow
This problem is currently the most common phenomenon in the use of air conditioners, and the user's reaction is also the strongest. There are several reasons for this problem:
1) The wind speed on the windward side is too large;
2) The surface cooler is in the negative pressure section, and no water seal is set when the unit leaves the factory;
3) The length and depth of the condensate tray are not enough.
As for the problem of excessive wind speed on the windward side, as mentioned above, for the determination of the height of the water seal set by the unit and the length and depth of the condensate tray, we should consult the manufacturer when ordering according to the negative pressure value of the cold section determine.
