The cascade refrigeration system is a freezing system that uses two kinds of refrigerants having different boiling points, which run through their own independent freezing cycle and are joined by a heat exchanger. This system is employed to obtain temperatures of -50 to -80°C or ultra-low temperatures lower than them. At such ultra-low temperatures, a common single-refrigerant two-stage compression system limits the low-temperature characteristics of the refrigerant to a considerably poor level, making the system significantly inefficient. The efficiency is improved by combining two kinds of refrigerants having different temperature characteristics. This system has the following advantages compared to a two-stage compression system:
•Energy is saved because the system allows the use of refrigerants that have suitable temperature characteristics for each of the higher-temperature side and the lower-temperature side.
•It allows stable ultra-low-temperature operation.
•The running cost is inexpensive.
•Repair is easy.
The Upper/Bottom cycle contains the following features:
1-Evaporator unit.
2-Compressor.
3-Condenser/Heat exchanger.
4-Expansion valve.
User can switch between these fluids:
1-R245a.
2-R1233.

**MatLab-SimuLink should be used to run the model.
Copyright © 2007 by Mohamed A. Sharaf Eldean Ayoub
All rights reserved. No part of this work may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher (Mohamed A. Sharaf Eldean Ayoub). For permission requests, write to the publisher, addressed “Attention: Permissions Coordinator,” at the address below.
 
REDS Software Library
https://www.redslibrary.com
Kuala Lumpur Malaysia
mohamedsheraf@redslibrary.com
00601139795943
All Rights Reserved
___________________