When the evaporator is circuited to provide counter flow of the refrigerant relative to the direction of the airflow, the superheat normally will have the least effect on evaporator capacity. Furthermore, suction pressure fluctuations will be minimized.
Refrigerant velocity inside the evaporator should be high enough to prevent excessive trapping of liquid refrigerant and oil, which may cause TEV hunting. Multi-circuited coils should be designed in such a manner that each circuit is exposed to the same heat load. Airflow across the coil must be evenly distributed.
Large capacity air-conditioning evaporator coils often are split into multiple sections so that one or more of these sections can be shut off for capacity control during part-load operation. Therefore, a TEV is required to feed each of these sections. The methods used to split these coils are referred to as: row split, face split, and interlaced.
Generally, TEVs will operate best on interlaced coils.
Source: Sporlan Valve Bulletin 10-9
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