Thermodynamic Analysis for Hybrid Low Temperature Sustainable Energy Sources in Cascade Heat Pump Technology

Abstract

<jats:p>A thermodynamic analysis of compound Cascade refrigeration system at low temperature heat sources was conducted. The analysis was based on a target temperature of hot water at the range of (60-70) °C out of the heat pump. The carrier thermal fluid temperature, which provides heat at the low temperature side of the Cascade system, determines the pair of refrigerants to be implemented. A hybrid heat pump design was proposed, which implements the sea water and ground as heat sources in a compound cycle. Two of refrigerant pairs were tested for the performance and energy efficiency comparison at fixed operating conditions. In the low temperature cycle, either R410A or R717 refrigerant was allowed to circulate and R134a is circulated at the high temperature cycle. The minimum isentropic efficiency of commercially available compressors was used in this investigation, a value of (70 %) was chosen. The results of the investigation revealed that R717/R134a exhibited a higher heating (COP) than that of R410A/R134a by (3 %). The results showed that increasing the isentropic efficiency of compressors to (90 %) improved the heating (COP) by (20 %) and minimized the power consumption by (24 %). The specific power consumed by compressors of the proposed system showed a decrease of upto (3 %) lower than that of the sea water base system.</jats:p>

Perspective Performance Evaluation Technique for a Cascade Heat Pump Plant Functions at Low Temperature Heat Source

“…The higher IT (35)°C showed lower power consumption than that of (33)°C for the whole range of test conditions. This was also confirmed by a number of previous studies conducted by [4] and [10][11][12]. The results revealed that R717/R134a at (33)°C IT has exhibited similar behavior and close numerical values to those of the R410A/R134a and R407C/R134a systems at IT of (35)°C.…”

“…The thermodynamic analysis was carried out on four refrigerant pairs, which have been believed to achieve the best performance in agreement with previous studies conducted by [4] and [10][11][12]. They are R410A/R134a, R407C/R134a, R717/R134a and R717/R600a at the specified operating condition stated in this work.…”

“…The previous work conducted by [4] and [10][11][12] was recalled for the present assessment where the best operating conditions and performance were attained. Hence, the following conditions were considered for the purpose of this study:…”

“…They concluded that at standard operating conditions, source (0)°C and sink (45)°C, efficiency and heating capacity improvements of up to (35%) achieved when the second heat source was at approximately (20)°C. A compound Cascade system was developed in [4] where three cycles were integrated with two low temperature heat sources. R717/R134a system exhibited COP increase of about (3%) higher than that of the R410A/R134a system for the whole test operating conditions.…”