Mehmet Direk

Energy and exergy analysis of an Automobile Heat Pump system

This study deals with energy and exergy analysis of an Automobile Heat Pump (AHP) system using R134a as the working fluid and ambient air as a heat source. An experimental AHP system consisting of original components from an Automobile Air Conditioning (AAC) system and some extra equipment was developed and instrumented. The system was operated in steady state under various ambient and return air conditions, while the compressor was driven at different speeds. The results show that the AHP can be used for supplementing the main comfort heating system of a vehicle producing insufficient waste heat.

Exergetic Analysis of a Gas Turbine with Inlet Air Cooling System

The climate condition affects the performance of the combined-cycle power plants. The efficiency of the combined cycle is significantly influenced by the temperature, pressure and humidity of the air. When the ambient air temperature increases, the density of the air decreases, and it leads to a reduction of power generated by the gas turbine. In this work, the energy and exergy analysis of a commercial gas turbine, with inlet air cooling, was performed. The effects of fogging system on gas-turbine performance studied. For this aim, the energy and exergy balances were obtained for each piece of equipment. Calculations have been made for four different cases for the regarded gas turbine system. Furthermore, exergetic efficiency, exergy destruction rates and improvement potentials were obtained, and the results of the study demonstrated graphically. It is concluded that the net power output of the gas turbine system increased at lower inlet temperatures and exergy destruction rates occurred from highest to lowest as combustion chamber (CC), gas turbine (GT) and air compressor (AC), respectively.

Design of an Inlet Air-Cooling System for a Gas Turbine Power Plant

In this study, the gas turbine cycle of Ovaakca power plant that is located in Bursa, Turkey was analysed. The aim of the study is to determine the use of an ice thermal energy storage system for the 239 MW-powered gas turbine cycle. The performance of the system was investigated for full-load conditions. Energy and exergy analysis were performed by using last decade’s meteorological weather data. The results showed that utilizing an ice thermal energy storage system can boost the net power up to 12.60%.

Theoretical Performance Analysis of an R1234yf Refrigeration Cycle Based on the Effectiveness of Internal Heat Exchanger

In this paper, the effects of internal heat exchanger (IHX) effectiveness on the performance parameters of the refrigeration cycle with R1234yf were theoretically investigated. For this purpose, a mathematical model was developed based on the energy balance of the cycle. The analysis were performed between -20°C and 0°C evaporation and 40°C and 50°C condensation temperatures based on the effectiveness value of IHX. The cooling capacity, coefficient of performance (COP), subcooling, superheat and compressor discharge temperature of the refrigeration cycle was examined. Finally, the performance results of the cycle with R1234yf were compared with the baseline cycle that utilizes with R134a. As a result, it was determined that the critical effectiveness to supply the same COP with R1234yf was determined 50% in comparison the baseline cycle. Keywords: R1234yf; R134a; Internal heat exchanger; Effectiveness DOI: 10.17350/HJSE19030000044 Full Text:

Evaluation of HFO-1234YF as a Replacement for R134A in Frigorific Air Conditioning Systems

The aim of this study was to compare and evaluate the frigorific air conditioning system using HFO-1234yf and R-134a as a refrigerant. For this aim, an experimental frigorific air conditioning system using both refrigerants was developed and refrigerated air was introduced into a refrigerated room. The performance parameters determined were the change of the air temperature in the condenser inlet and time. The performance of frigorific air conditioning system has been evaluated by applying energy analysis. Experiments were conducted for a standard frigorific air conditioning system using the R134a as a refrigerant. Airflow has been introduced to the refrigerated room for 60 min for each performance test. From the result for both refrigerant, the temperature gradient in time was comparable. The HFO-1234yf refrigerant can use the standard frigorific air conditioning system that is currently being used by the R134a refrigerant, without any changes needing to be made.

Energy and Exergy Analysis of an R134A Automotive Heat Pump System for Various Heat Sources in Comparison with Baseline Heating System

Performance of an automotive heat pump (AHP) system using R134a and driven by a diesel engine has been evaluated in this study. For this purpose, an experimental AHP system capable of providing a conditioned air stream by utilizing the heat absorbed from the ambient air, engine coolant and exhaust gas was developed. The experimental system was equipped with instruments for measuring engine torque and speed, refrigerant and coolant mass flow rates, refrigerant and air temperatures as well as refrigerant pressures. The system was tested by varying the engine speed, engine load and air temperatures at the inlets of the indoor and outdoor coils. Using experimental data, an energy analysis of the system was performed, and its performance parameters for each heat source were evaluated for transient and steady-state operations. Then, the performance of the AHP system for each source was compared with that of the system using other heat sources and with that of the baseline heating system. The investigated performance parameters include air temperature at the outlet of the indoor coil, heating capacity, coefficient of performance and exergy destruction rates in the components of the AHP system. The total exergy destruction rate in the AHP with engine coolant is higher than those in the AHP with ambient air and with exhaust gas mainly because of the greater refrigerant mass flow rate and heating capacity.