|Abstract:||A refrigerant-side instrumentation system has been developed, installed, and utilized to
obtain steady-state data from a 1.5-ton capacity room air conditioner for the continued validation
of a simulation model. This report describes the design, in situ calibration, and verification of
three venturi meters used to provide minimally intrusive measurements of refrigerant mass flow
rate in the discharge, liquid, and suction lines. The specification and implementation of
immersion thermocouples and pressure transducers used to directly measure refrigerant
. temperatures, absolute pressures, and pressure drops is also described. Using companion data
from thennocouples affixed to refrigerant tube surfaces, comparisons are made between surface
and refrigerant-side instrumentation methods and recommendations are given regarding the
simplest, cheapest, and most accurate methods for measuring refrigerant temperatures, pressures,
and mass flow rate in room air conditioners. As well, the intrusive effects of refrigerant-side
instrumentation on room air conditioner perfonnance are investigated. Lastly, perfonnance tests
using R407C, a promising alternative to R22 in room air conditioners, are reported for the
purpose of validating the simulation model with alternative refrigerants.
The venturi meters provided refrigerant mass flow rate within ±2% and revealed that the
discharge and liquid lines are best suited for venturi mass flow measurements. With the proper
installation and insulation, surface thermocouples can be used to provide refrigerant temperatures
within ±1-2 OF for the two-phase regions and outlets of the condenser and evaporator.
Unavoidable intrusions on room air conditioner performance are introduced by the instruments
themselves and the process of installing them (cutting open tubes, removing and reinstalling
compressor, etc.). The effect of increased system volume can be controlled by increasing charge.