Heat Transfer Studies on a Forced Convection Loop with Biphenyl and Biphenyl Polymers

Abstract

Heat Transfer Studies on a Forced Convection Loop with Biphenyl and Biphenyl Polymers number of liquid organic materials have been used as heat transfer media at temperatures to about 600°F. for a number of years. More recently certain stable aromatic and alkyl-aromatic compounds, such as biphenyl, terphenyl mixtures, and monoisopropylbiphenyl, have been considered for possible primary coolants at temperatures to about 800°F. These materials have poorer heat transfer properties and stability than water; however, their relative inertness to container materials and high boiling temperatures make them attractive for many applications.

Heat-Transfer Studies on Some Stable Organic Fluids in a Forced Convection Loop.

“…The reliability of a general correlation is dependent upon the accuracy of the physical property values as well as the film coefficient values and the form of the correlation. The values of density and viscosity are considered acceptable since values for the polyphenyl fluids measured here and by other workers (13,19) are in agreement. Although specific heat values for each of the polyphenyl fluids were not measured, and exact compositions of the irradiated fluids were not known, the specific heat study of phenyl compounds by Walker (21) made in conjunction with this work, permits an acceptable estimation for these fluids.…”

“…This difference was reproducible and was related to fluid velocity, heat flux, and temperature difference (£s -U). Earlier work (19) showed that the same average linear temperature profile was obtained with couples located along the top and bottom of a tube, as with couples located along the top, bottom, and each side. In this study, couples were positioned on the top and bottom to give an average linear temperature profile, from which the average outside-wall temperature, tw, was determined at the mid-point of each 12-inch measurement section.…”

“…Film coefficient data for the two irradiated fluids indicated a fouling of the heat-transfer surfaces, but the scale was identified as lead and lead oxide by x-ray analyses. This fouling resulted from a lead contamination of the loop which occurred during previous studies with biphenyl polymers that contained lead as an impurity (19). As (Continued on page 524) reported in that study, scale could be removed with warm acetic acid or could be swept out at fluid velocities of 20 to 30 feet per second.…”

“…This is the same temperature dependency which has been observed by Sakiadis and Coates (17) for a number of organic fluids at lower temperatures, by Briggs (5) for biphenyl to 245°F., and recently by Kerzhentsev and Vargaftik (10) for Dowtherm A to 572°F. The values of conductivity used in correlating the previously published results for biphenyl (19) and (20) were values obtained as part of a preliminary engineering study (13). There was little or no change of conductivity with temperature in these values.…”

“…The heat-transfer loop constructed for this study and described previously (19) consisted essentially of pump, a flow-control system, a preheater unit, a gas-separator unit, a heat sink, a surge tank, and a make-up tank. Low-carbon steel pipe (welded) was used in the system with the exception of the test section which was made of Stainless steel, Type 347.…”