Thermodynamic analysis of optimal condensing temperature of cascade-condenser

jerryxie2004

Thermodynamic analysis of optimal condensing
7 m* M  m: K4 l$ Y  q2 Xtemperature of cascade-condenser in CO2/NH3
cascade refrigeration systems
/ X0 W6 `- E9 C9 g. ~Tzong-Shing Lee*,1
9 \, [" ^$ J% U: g/ \2 F, Cheng-Hao Liu, Tung-Wei Chen
Department of Air-Conditioning and Refrigeration Engineering, National Taipei University of Technology,
No. 1, Sec. 3, Chung-Hsiao East Road, Taipei 106, Taiwan
Received 10 November 2005; received in revised form 6 March 2006; accepted 6 March 2006
Available online 5 June 2006
Abstract
9 J2 @/ K  ^! U) kThis study thermodynamically analyzed a cascade refrigeration system that uses carbon dioxide and ammonia as refriger-
ants, to determine the optimal condensing temperature of the cascade-condenser given various design parameters, to maximize
# d( V  F+ H2 V: Rthe COP and minimize the exergy destruction of the system. The design parameters include: the evaporating temperature, the
condensing temperature and the temperature difference in the cascade-condenser. The results agreed closely with the reported
8 E5 p/ N. Z+ j& t# S; {0 ^experimental data. The optimal condensing temperature of the cascade-condenser increases with TC, TE and DT. The maximum
9 w: q3 ^+ u  r# ECOP increases with TE, but decreases as TC or DT increases. Two useful correlations that yield the optimal condensing temper-
; j) \' K9 x2 s; a) Z) q1 tature of the cascade-condenser and the corresponding maximum COP are presented.

2006 Elsevier Ltd and IIR. All rights reserved.
- z3 ^: f+ g! T+ eKeywords: Refrigeration system; Compression system; Cascade system; Ammonia; Carbon dioxide; Optimization; Temperature; Condensa-
tion; COP