Torsten Heinemann

Vapor-phase thermal conductivity of 1,1,1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,2,2,3-pentafluoropropane and carbon dioxide

Abstract The insulation efficiency of polyurethane foam is mainly (60 to 65%) determined by the thermal conductivity of the cell gas, which is a mixture of carbon dioxide (CO 2 ) and a blowing agent. Until recently CFC-11 (trichlorofluoromethane) was the most widely used blowing agent. To find adequate substitutes for CFC-11, the vapor-phase thermal conductivity of several potential blowing agents has been measured. The experimental procedure is based on the transient hot-wire method. The apparatus was designed in cooperation with the University of Stuttgart (Prof. K. Stephan). The measuring cell (stainless steel, 1.4571) with a length of 270 mm and a diameter of 48 mm consists of two parallel chambers with platinum wires of different lengths. In this paper experimental results for the vapor-phase thermal conductivity of carbon dioxide (CO 2 ), 1,1,1,2,2-pentafluoropropane (HFC-245cb), 1,1,1,3,3-pentafluoropropane (HFC-245fa), and 1,1,2,2,3-pentafluoropropane (HFC-245ca) are given. Experiments have been performed at pressures between 0.2 MPa and 1.5 MPa and temperatures between 298 K and 419.91 K.

Experimental Determination of the Vapor Phase Thermal Conductivity of Blowing Agents for Polyurethane Rigid Foam

Blowing agents are mainly responsible for the insulation properties of polyurethane rigid foams. Detailed knowledge about the vapor conductivity of blowing agents and their mixtures is essential for their basic understanding. In addition to their insulation properties, blowing agents to a large extent determine the mechanical properties of the foam. Today, blowing agent mixtures are often used in an attempt to combine both worlds, low thermal conductivity and high vapor pressure at low temperatures. Our investigations aim at a better understanding of the relevant practical properties of blowing agents and their mixtures and to focus on their meaning for actual and potential foam systems of interest to the rigid foam insulation market. A newly developed transient hot wire method was used to determine the vapor phase thermal conductivity of various blowing agents used in rigid polyurethane foam. Data for CFC-11, HCFC-141b, HFC-365mfc, HFC-356mffm, HFC-245fa, HFC-245ca, cyclopentane, isopentane, n-pentane, isobutane, n-butane, and carbon dioxide have been generated. In addition to measurements of the pure compounds, current market mixtures of cyclopentane with low boiling hydrocarbons have been investigated. Experiments have been performed at pressures between 0.2 MPa and 1.5 MPa and temperatures between 298 K and 421 K.