Abstract: The present investigation deals with the performance assessment of Cascade heat pump plants. The overall power consumption for a Cascade system for typical heat pump characteristics was studied. Four environment friendly refrigerant pairs R717/R134a, R410A/R134a, R407C/R134a, and R717/R600a were investigated at low temperature cycle (LT) evaporator and high temperature cycle (HT) condenser temperatures of (-15 to -4)°C and (70)°C respectively. A preliminary heat pump plant is suggested to produce (500) kW heat output load as hot water demand at (65)°C with (25)°C temperature lift and a proper circulation rate. The investigation was carried out at cascade heat exchanger intermediate temperature (IT) of (33)°C and (35)°C. Sea water at (7)°C was used as a sustainable low temperature heat source and (30%) ethylene glycol-water brine at temperature of (5)°C as a thermal fluid heat carrier at the LT cycle evaporator. The evaluation of the thermal performance of the refrigerant pairs was based on a fixed heat pump extraction load at the LT cycle. The heat pump heating coefficient of performance (COP) revealed an increase fell within the range of (5-7.5)% higher than that of the plant heating COP value for the studied refrigerant pairs at the whole investigated operating conditions range. The higher IT exhibited the highest heat pump and plant heating COP than those at the lower value. R717/R600a showed the highest heating COP, lower power consumption and lower global warming potential (GWP) among other investigated refrigerant pairs. The power consumed by auxiliary pumps to circulate thermal fluid heat carriers through a heat pump may account to (4-4.5)% and (2-3)% of the extracted and output heating loads respectively, higher values could be expected for real plant. Two polynomial correlations for the assessment of the pumping power in terms of the extracted and output heating loads were derived from the present work.Abstract: The present investigation deals with the performance assessment of Cascade heat pump plants. The overall power consumption for a Cascade system for typical heat pump characteristics was studied. Four environment friendly refrigerant pairs R717/R134a, R410A/R134a, R407C/R134a, and R717/R600a were investigated at low temperature cycle (LT) evaporator...Show More
Abstract: This paper aspire in evaluating the impact of Ethiopia’s productive safety net program on households’ livelihood in Babile district by using primary data that were collected during January and February in 2017 from PSNP treatment and controls group sampled households. Descriptive statistics and Propensity Score Matching were used to evaluate the impact of the program in the study area. The paper revealed that among eleven model variables five of them influence the program participation decisions. Thus, the program had positive and highly significant effect on consumption in which 1269.11 Kcal was found due to the program intervention. Even though the result of the study shows that there is no significant difference among treatment and control groups in terms of annual income household participation in PSNP has positive and statistically significant effect on food consumption, so that on households’ livelihood.Abstract: This paper aspire in evaluating the impact of Ethiopia’s productive safety net program on households’ livelihood in Babile district by using primary data that were collected during January and February in 2017 from PSNP treatment and controls group sampled households. Descriptive statistics and Propensity Score Matching were used to evaluate the im...Show More
