Alican Çebi

A Theoretical Comparative Study on Nanorefrigerant Performance in a Single-Stage Vapor-Compression Refrigeration Cycle

The topic of nanofluid heat transfer is certainly of interest to the heat transfer community. Nanorefrigerants are a type of nanofluids that are mixtures of nanoparticles and pure refrigerants. This paper focuses on five different nanorefrigerants with Al2O3 nanoparticles and their pure fluids: R12, R134a, R430a, R436a, and R600a. The coefficient of performance (COP) and compressor work for various evaporation and condensation temperatures are investigated. A method is developed to estimate the performance characteristics of nanorefrigerants in the refrigerant cycles for the nonsuperheating/subcooling case and superheating/subcooling case. The enthalpy of nanorefrigerants is obtained through the density. The validation process of the proposed method was accomplished with the available data in the literature. The results indicate that COP is enhanced by adding nanoparticles to the pure refrigerant and maximum values obtained using the R600a/Al2O3 mixture.

A Focus on the Literature Review of Nanorefrigerants

The heat transfer performance of various thermal devices can be augmented by active and passive techniques. One of the passive techniques is the addition of nanoparticles had the size of 1 and 100 nanometers to the common heat transfer so that the thermal transport properties of the prepared suspension called nanofluid will be enhanced compared to the base fluid. Nanorefrigerants as a special type of nanofluids which are mixtures of nanoparticles and refrigerants have a wide range of applications in diverse fields such as refrigeration, air conditioning systems and heat pumps. In this study, the missing points on this new method are also indicated regarding the lack of studies on the determination of physical properties of nanorefrigerants and the flow of nanoparticles.Copyright

Refrigerated Railroad Car Design for Shipping Frozen Meat Using Alternative Refrigerants

Refrigerated railroad cars, known as reefers, are railroad rolling stock designed to carry perishable freight at specific temperatures. They are insulated boxcars that keep the cargo at a regulated temperature. As soon as railroad cars had the capability to keep a load cold, the potential growth of the meat, dairy, fruit and brewery industries became nearly unlimited. In this paper, a cold-room system in a railroad car was investigated as a case study to illustrate the use of the sample model. The change of substitute refrigerants and insulation thickness of the cold rooms’ refrigeration system was also considered in the model. The coefficient of performance (COP), refrigerant flow rate and capacities of each component of the refrigeration system were calculated for the refrigerants R12, R22, R134a, R290, R410A, R430A, R431A, R436A, R507A, R600a as part of this analysis. As a result of the energy analyses, all of the substitute refrigerants have a slightly lower COP and require higher compressor work than R12 and R22 for a condensation temperature of 40°C. The frozen meats have an evaporation temperature of −25°C related to the preserved product in the case studies. Influences of the insulation thickness of the wall on evaporator capacity and outside temperature of various cities on the condenser are also studied.Copyright

Effect of the Heat Recovery System to the Performance of Air Handling Unit of a Workplace

This study investigated heat recovery systems and its effects on energy saving. Heat recovery systems are used for energy saving in heating, ventilating and air conditioning applications. In the study, a workplace equipped with and without heat recovery system was taken into consideration. The workplace has an air handling unit (AHU) which has 25,000 m3/h fresh air flow rate, 414 kW heating and 356 kW cooling capacities. AHU uses mixture air including %50 rooms air and mixes in mixing filter section. As a heat recovery system, rotary type heat exchanger was selected and its performance was investigated. Annual energy saving, initial investment cost, annual operating expenses, payback time and profit parameters were calculated to compare two air handling units for each month. According to the results, cooling battery power in the cooling season and heating battery power is reduced with the usage of rotary type heat exchanger. It is obvious that presence of the heat recovery systems enhances performance of the air handling units.Copyright

Thermodynamic Analysis of Solar Heat Pump Assisted Heating Systems

In this study, a system has been developed which can be used for heating buildings by utilizing solar energy, which is free and abundant in our country, with the aim of minimizing fossil based fuel consumption especially at wintertime and this system’s efficiency has been analyzed mathematically with numerical methods.First of all, in this study the performance of a solar heat pump system is examined. The city of Antalya is chosen for this study which is in the southern region of Turkey with an abundant source of solar energy. The usability of solar energy throughout the year is examined and its application areas in building heating with the utilization of heat pumps are determined. In addition an auxiliary system with an alternative energy source is considered in case solar energy is insufficient by itself.In order to determine all of the above, energy analysis of the system is performed. The advantages of the solar heat pump heating system are studied considering the amount of energy saved and the efficiency of the system. Thermodynamic and thermoeconomic analysis has been carried out in order to determine how effectively the solar energy is utilized by the system and the advantages of solar heat pump.Copyright

Performance Comparison of Various VRV Systems for a Bank Application

In heating and cooling applications, VRV (Variable refrigerant volume) systems can be used instead of air handling units because of their low energy consumption. In this study, a bank which is kept 20°C and 24°C inside temperature heating and cooling seasons respectively was taken into consideration in order to compare different VRV systems such as VRV system for heating only mode and VRV system supported with heat pump mode device. The heat loss from bank was calculated by considering heat loss from walls, air alteration and heat sources such as human, light, devices used in the space. The outdoor integrated heating and cooling capacity calculations were performed by means of commercial software for seven different climate regions in Turkey. R410a was selected as the refrigerant of investigated VRV systems because of its low ODP (Ozone Depletion Potential) and GWP (Global Warming Potential) values and actual common usage. Effect of outside air temperature, evaporation temperature of refrigerant and outdoor unit location (such as high level, same level and lower level) on the performance of VRV systems was considered in calculations. The calculations are performed in order to clarify of effect of outdoor unit level. Payback time is calculated as 4.5 months for usage of VRV system instead of air handling unit.Copyright

Determination of Pressure Drop of Pure Water Flowing Upward Direction in a Double Tube Heat Exchanger Having Smooth and Microfin Tubes

Single phase friction factor and pressure drop behavior of smooth and microfin tubes are studied experimentally. The vertical test section was working as a counter flow double tube heat exchanger with water flowing in the inner smooth and microfin tubes having varying inner diameters and cooling water flowing in the annulus. Pressure drop of water due to cooling in upward flow in inner tubes is determined by experiments. Inner tube mass flow rate was between 0.023 kg/s to 0.100 kg/s while test section inlet temperatures were 40°C and 60°C. Effect of Reynolds number on pressure drop is also investigated and Blasius type friction factor correlations are developed for both smooth and microfin tubes.Copyright

Fundamental Basis and Application of Cold-Room Project Design: A Case Study of Frigoship

In this paper, a cold-room system in a frigoship was analyzed as a case study to demonstrate the application of the proposed model. The model was also evaluated in terms of the alteration of alternative refrigerants and insulation thickness of the cold rooms’ refrigeration system. The coefficients of performance (COP), refrigerant charge rates, and capacities of each component of the refrigeration system for the refrigerants CFC-12, HCFC-22 and their alternatives, such as HFC-134a, HFC-410a, HFC-404a, HFC-407c, and HFC-507 were determined by considering the effects of the main parameters of the performance analysis, such as refrigerant type, Based on the results of the energy analyses, all of the alternative refrigerants have a slightly lower COP and require higher compressor work than CFC-12 and HCFC-22 for condensation temperature of 40°C. The hunted fishes have an evaporation temperature of −25°C regarding with the preserved product in the case studies. Effects of isolation thickness of wall on evaporator capacity and sea water temperature on condenser are also investigated. Also variation capacity of system components such as evaporator, condenser and compressor with relative humidity of neighbor volume is studied.Copyright