|Title:||Simulation Analysis of Thermal Systems and Components
|Author(s):||Jain, G.; Bullard, C.W.
|Subject(s):||stationary air conditioning system analysis
|Abstract:||Issues involved in the solution of thermal system problems within a Newton-Raphson framework have
been addressed. The physical limitations of Newton-Raphson variables and limited range of thermodynamic
property calculation routines were identified as key factors in the stability and robustness of the solution algorithm.
A general guideline is presented to be used while solving thermal system problems.
A validation study for two R134a condensers and one 3 slab CO2 gas cooler was done using finite volume
based heat exchanger models. The finite volume sequential marching algorithm resulted in excellent agreements
with the heat transfer data (within ±5%). The models however underpredicted refrigerant side pressure drop by as
much as 80% for the gas cooler and by 50% for the condensers. Nitrogen flow tests were conducted and it was
found that for single-phase flow the steeplechase arrangement of microchannel tubes in the headers contribute about
10% to the total pressure drop. Through a systematic analysis the observed discrepancies in pressure drop were
attributed largely to the effect of high quantity of oil present in the gas cooler. The interaction of two-phase
refrigerant with microchannel headers and oil were suspected to be the possible reason for the same in R134a
The effect of capillary tube-suction line heat exchanger (ctslhx) geometry on system performance was
explored at various design and off-design conditions by embedding it in a system model. A detailed finite-volume
model of the capillary tube and suction line, capable of handling all the phase-change complexities was used. All the
ctslhx configurations considered meet the design constraints and had little effect on the design COP. Captubes with
large inlet sections and relatively small outlets were found to give best performance at all the simulated off-design
|Publisher:||Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
|Series/Report:||Air Conditioning and Refrigeration Center TR-235
|Sponsor:||Air Conditioning and Refrigeration Project 69
|Date Available in IDEALS:||2009-06-22