THE UN I VE RS IT Y OF M I C H I GAN COLLEGE OF ENGINEERING Department of Mechanical Engineering Interim Report COMPARATIVE RATINGS OF TWO FREON (F-12) AIR-COOLED CONDENSERS OF DIFFERENT DESIGN *"' Frederi-ck K. Boitwell Assistaft'"Professor of. Mechanical Engineering R. Clay Porter P6tfess.or. of Mechanical Engineering, F; r.& ckrederickJ0 Vesper Ass istatil"-Profesor: of Mechical Engineering UMRI Project 2940 under contract witho Karmazin Products Company Wyandotte, Michigan administered by: THE UNIVERSITY OF MICHIGAN RESEARCH INSTITUTE ANN ARBOR March 1960

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OBJECTIVE The objective of this report is to present the results of a single phase of the research program now in progress for the Karmazin Products Company. Specifically, it describes the heat-transfer characteristics of two air-cooled refrigerant condensers when tested in accordance with a given standard. PROGRAM As a part of The University of Michigan Research Institute Project 2940, the units described below were tested according to the following standard test conditions. Dry-bulb temperature entering unit 95~F Dry-bulb temperature of ambient air 95~F Saturation temperature of refrigerant vapor entering cordenser 105~F Actual temperature of refrigerant vapor entering condenser 1700F + 10 Liquid refrigerant sub-cooling at condenser outlet 5~F max The condenser units are identified in this report as follows: Unit A Unit B 3/8-ino-diameter tube 11/32-in.-diameter tube 66 fins 6e fins 10 x 10-5/16-in. face dimension 10 x 10-5/16-in. face dimension 1-156-in. depth 11/16-in. depth Under the conditions of the test, the two units were tested individually, each with the same air fan and cowling to establish commnaon air flow through the condenser sectiors. TEST SETUP AND PROCEDULE A complete refrigeration system consisting of a reciprocating compressor, refrigerant temperature control, condenser, receiver, expansion valve, and evaporator was set up for this test. The components are shown schematically in Fig. 1. 1

To make a test, the system is bled thoroughly to remove all traces of air, the compressor is started, and the flow rate and temperature controls are regulated until equilibrium conditions are insured for the test conditions specified in the program. When equilibrium conditions have been established, a data run is made. A data run consists of a period of maintaining test conditions within the allowable limits for a period of from 50 to 90 milnutes without interruption. Data are recorded for every 10-minute inte-rval. During a run the freon is condensed in the test unit and is drained into a receiver mounted on the platform scales. A fixed liquid level is maintained in the sight glass (see Fig. 1) by adjustment of the condensate drain valve. Since the lines leaving the condenser unit are well insulated, only that liquid condensed in the condenser is weighed. Since the weight and time fo3 collection is known, the pounds per hour of freon condensed can be calculated, and from this, by use of tables of freon properties, the heat-removal rating of the condenser units can be evaluated. RESULTS The results of these tests are as follows: Unit A Unit B 3/8-in.-diameter tube 11/32-in.-diameter tube 66 fins 62 fins 711 Btu/hr 775 Btu/hr 10.6 lb/hr, freon condensed 11.45 lb/hr, freon condensed C ONCLUS IONS These results indicate: (a) Unit B (11/32-in.-diameter tube, 62 fins) has a higher condensing rate by almost 8 to 10o. (b) Unit B should operate with a lower compressor head pressure than Unit A when under the same refrigeration load on a given systenm.

NOTE CONDENSE, DOTS INDCKAE THERWXCDUPLE / A PRE55URE LOCATION M A1N0M ET I LASS EVAPORATOR' EXPANSION COOTROLi COKOENS AE VALVEV IVALVE5-. |RAIN VALVE RECEIVER DRYI PRLURI IL I (AGE.5CALE 1-. - GAE,,o Fl GURE 1

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