Direct Expansion Air Conditioner
By M. Brandemuehl for ASHRAE
Revised for TRNSYS by N. Blair and R. Schwarz

      	This model was adapted strictly for use with the TRNSYS Program by
the Solar Energy Laboratory.

	A unitary direct expansion (DX) air conditioner is modeled based on the 
approach used in the DOE 2.1 building simulation program.  The capacity, 
coefficient of performance and sensible heat ratio are specified at ARI (Air 
Conditioning and Refrigeration Institute) rating conditions of 95F outdoor 
temperature, 80F evaporator air dry bulb and 67F wet bulb temperature, and 
airflow of 450 cfm/ton of rated capacity.  The model calculates coil outlet 
conditions and compressor section power consumption at off-design conditions of 
all four rating variables using SUBROUTINE DXDOE.  The algorithm does not
account for the thermal effects or power consumption of the indoor fan.  While
the standard DOE 2.1 approach calculates coil capacity as a function of
evaporator wet bulb temperature, this algorithm recognizes that dry coil
performance is a function of dry bulb temperature.  If the correlations
calculate the sensible capacity to be greater than total capacity, performance
is iteratively determined to achieve consistency between the DOE 2.1
correlations and the physical dependence on dry bulb temperature.

REF:A Toolkit for Secondary HVAC System Energy Calculations  May 25, 1992
    Joint Center for Energy Management  University of Colorado at Boulder