Six studies of drying kinetics were done on automotive air-conditioning systems from 1978 to 1985. These studies have been reviewed in order to rate various drier designs and locations. The parameters tested were:

- High pressure vs. low pressure location
- Type 4A molecular sieve vs. silica gel
- Vapor vs. liquid phase
- Flow path through vs. by the desiccant

The studies were done in the laboratory on an automotive air-conditioning system and a liquid-refrigerant circulating system. Drydown time constants for each system and mass transfer coefficients for the drying of refrigerant 12 were determined. The receiver/dehydrator design (high side, liquid phase, flow-by) had the most rapid drydown rate. Its drying rate was two orders of magnitude faster than the slowest design, the accumulator/drier (low side, liquid phase, flow-by). A modified accumulator with a vapor phase flow-through drier had an intermediate drydown rate. Type 4A molecular sieve was about four times faster than silica gel.

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