Vapor-Phase Thermal Conductivity of Binary Mixtures of Cyclopentane and R134a with R365mfc

The thermal conductivity of mixtures of R365mfc (1,1,1,3,3-pentafluorobutane), with R134a (1,1,1,2-tetrafluoroethane) and cyclopentane were measured using a transient hot-wire method, in the pressure range between 0.1013 and 0.7 MPa and temperatures between 311 and 413 K. The composition of the measured mixtures was 93.0% R365mfc + 7.0% R134a (kg/kg), 27.0% R365mfc + 73.0% R134a (kg/kg) and 62.8% R365mfc + 37.2% Cyclopentane (kg/kg). The Wassiljewa mixing rules modified by Mason and Saxena and the Extended Corresponding States Theory were used to correlate and to predict the experimental results obtained, with an average absolute deviation of 1.8 and 10%, respectively.

Aging of Rigid Polyurethane Foams: Thermal Conductivity of N2 and Cyclopentane Gas Mixtures

The thermal conductivity of three mixtures of nitrogen and cyclopentane is measured using a transient hot wire method, at temperatures between 315.14 and 395.89 K, and pressures up to 0.53 MPa. These mixtures are important in the evaluation of the evolution of the thermal insulation capacity of closed-cell polyurethane foams considering their aging during the respective applications’ total life time. The experimental thermal conductivity data are correlated with the Wassiljewa mixing rules as modified by Mason and Saxena, and predicted using extended corresponding states theory (ECST), with an average absolute deviation of 1.1 and 8.9%, respectively. The increase of the nitrogen fraction in cyclopentane-nitrogen mixtures leads to higher thermal conductivity values than has been predicted by ECST using only pure component thermal conductivity data for all measurements.

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.