Accession Number : AD0695316

Title :   STUDY OF HEAT LOSS AND HYDRAULIC RESISTANCE OF LONGITUDINALLY FINNED SURFACES,

Corporate Author : FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO

Personal Author(s) : Kurylev,E. S. ; Ramadan,A. M. ; Evreinova,V. S.

Report Date : 30 JAN 1969

Pagination or Media Count : 13

Abstract : Heat exchangers with long lengthwise ribs are in practical use. The literature, however, contains no data on the effect of the size of breaks between ribs on the turbulization of flow and reduction of the thickness of the boundary, and consequently also on the size of the heat transfer coefficient. These problems are the object of the present study. At the same time the effect of the breaks between the ribs along the channel on the aerodynamic drag of the equipment was studied. Several versions of longitudinally ribbed surfaces were studied, but in all the rib thickness was 0.2 mm, height 30 mm, and spacing 3 mm. The unbroken ribs were the control; the broken and slanted ribs were the experimental objects. A specially designed setup was used for the study and the following parameters were measured: drop in pressure head of air through windbox, air temperature at inlet and outlet of heat exchanger, air temperature before diaphragm in device, air temperature within windbox and ribbed surface at three positions (rib base, middle rub, and rib top) temperature of rib surface at the same three points, water temperature at inlet and outlet of water box, water consumption. It was found that for ribs, the ratio of whose channel length to equivalent diameter was greater than or equalled seven, the optimum break between rows of ribs over the length of the channel was 3--4 mm. Increasing the break had practically no effect on degree of heat transfer and hydraulic drag. In order to reduce the dimensions of the heat exchanger the break may be reduced, but then the rows of ribs interrupted by the breaks must be alternately perpendicular and at an angle to the base. (Author)

Descriptors :   (*HEAT EXCHANGERS, FINS), (*FINS, HEAT TRANSFER), (*DRAG, FINS), BOUNDARY LAYER, HYDRAULIC EQUIPMENT, THICKNESS, AERODYNAMIC CHARACTERISTICS, USSR

Subject Categories : Air Condition, Heating, Lighting & Ventilating
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE