Coil air bypass and chilled water flow control are common means for controlling space temperature in air-conditioning systems during part-load operation. Sometimes this results in extreme changes of relative humidity, which can cause discomfort in the conditioned space. This situation was investigated by using an improved microcomputer model for cooling/ dehumidifying coils. As the load in the space drops off, two separate control strategies were considered: (1) Modulating the chilled water flow rate and (2) varying the percent bypass air. Although the load at the coil was about 11% greater for bypass air control when compared to chilled water control for the part-load range considered, much better control of the relative humidity and comfort condition was obtained with the former. As the Design Sensible Heat Ratio (DSHR) decreased with corresponding increased latent loads, it was necessary to have lower values of coil discharge air temperature for adequate dehumidification.
Units: I-P
Citation: Symposium, ASHRAE Transactions, 1987, vol. 93, pt. 2, Nashville, TN
Product Details
- Published:
- 1987
- Number of Pages:
- 13
- File Size:
- 1 file , 1 MB
- Product Code(s):
- D-NT-87-17-2
