Search

In this study, the performance of a case study of Organic Rankine Cycle with heat recovery exchanger using different fluids is analyzed. As the fluids worked in the cycle, the commonly used R134a, R236fa, R245fa, R600a, R717 and R718 are preferred. Cycle performances of the selected fluids are compared based on both the heat source's temperature that changes between 80°C and 109°C and the effectiveness of the heat exchanger. Furthermore, the contribution ratios and the order of importance of the parameters affecting the performance of the cycle are evaluated using the Taguchi statistical method. As a result, the effect of the waste-heat source temperature on the performance of the system is greater than the other parameters examined, and the contribution ratio of this parameter is determined as 59.80%. However, effectiveness of heat exchanger is found to be the least effective parameter and the effect ratio is calculated as 2.18%. In addition, the best and worst operating conditions are determined from the statistical analysis, and in these conditions, the thermal efficiencies of the Organic Rankine Cycle are obtained as 15.26% and 8.61%, respectively. [ABSTRACT FROM AUTHOR]

Condensation, which is the result of water vapor diffusion, affects the heat transfer in the building material negatively. The condensation which is seen mostly in winter seasons at building materials, occurs when the surface temperature of the building material in contact with air falls below the raw temperature of the air. In this case, condensed water may cause mildew, fungal growth, odors, and deterioration of dye and building materials or adversely affected thermal insulation on the walls. Materials used for thermal insulation in buildings constitute resistance against water vapor diffusion. Water vapor diffusion resistance factor (VDRF) of materials can vary over a wide range. In this study, considering VDRF range that is commonly encountered in insulation applications, the effect of VDRF of insulation materials on condensation within constructions, and on the minimum thickness of insulation required to prevent this condensation accordingly were examined. Externally insulated wall was taken as sample wall model, heat and mass transfer calculations from wall unit area and insulation thickness minimization were performed for different indooroutdoor temperatures and relative humidity values. As a result of the analysis conducted, in constant indoor-outdoor conditions in general, as VDRF increases, the risk of condensation inside the wall first decreases and then increases. Minimum insulation thickness that is required to be applied to prevent condensation also shows a similar trend depending on the VDRF. For constant VDRF, it was come to the conclusion that as the difference between indooroutdoor temperatures and relative humidity increases, the risk of condensation and consequently required insulation thickness increases. [ABSTRACT FROM AUTHOR]