Sharif Digital Repository

In this study the first and the second laws of thermodynamics are evaluated for a single effect absorption chiller. Entropy generation and COP are selected as the objective functions and their variations are studied by varying the generator temperature for various condensing temperatures. For this purpose, the enthalpy and the entropy data of the super-heated steam, saturated steam and the saturated water are formulated in the mathematical equations. Also to provide the required steam of generator, prime mover in the form of internal combustion engine is applied and its partial load conditions are analyzed. A residential tower is considered as the case study for selecting the proper prime... 

In this research the performance of a U-shaped pulsating heat pipe (PHP) was investigated using numerical methods. This heat pipe consists of two sections: The evaporator is set at the two ends of the pipe, and the middle part of the pipe comprises the condenser section. This heat pipe is a type of open looped pulsating heat pipe. The governing equations are derived analytically from the continuity, momentum, and energy equations and are solved implicitly. In this model, considering the liquid mesh, the rate of convection and boiling heat transfer in the U-shaped PHP, which has not been investigated as of yet, are examined. The effect of the evaporator temperature on the pulse amplitude and... 

Exploration of the ejector refrigeration cycle (ERC) in the combination with well-known power cycles to produce cooling output as well as power output is highlighted in recent decades. Since organic Rankine cycle (ORC) is practically usable than other power cycles, a combination of the ORC/ERC in a novel form is presented. Power and refrigeration sub-cycles are combined by a common condenser in separate loops to form dual-loop power/refrigeration cycle. The exhaust of the turbine is mixed with the outlet flow of the ejector, and then the mixed flow is fed into the condenser. Thermodynamic and thermoeconomic analysis of the proposed cycle are carried out with different working fluids (i.e.,... 

The effect of working fluid inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working fluid inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different... 

In this paper, the effect of different parameters on the thermal operation of a Closed Loop Pulsating Heat Pipe (CLPHP) has been investigated. These parameters include the working fluid, the inclination angle, the filling ratio, and the input heat flux. The effect of nanoparticle mass concentrations has been analyzed as well. It was observed that the CLPHP can decrease thermal resistance up to 11.5 times compared to the same empty copper tube with thermal resistance of 9.4 K/W. Optimum thermal operation for a system with the water-silver nanofluid was achieved at conditions of the 50% filling ratio with thermal resistance of 0.9 K/W, and for the water-titanium oxide system, the optimal... 

Engines that extract energy from low-grade heat sources, e.g., from other processes, have received considerable attention recently. The use of Fluidyne, which is a liquid piston Stirling engine, is quite popular. Herein, we explore the use of liquid-to-vapor phase change in a Fluidyne. This provides two considerable differentiators; (1) exploitation of very low temperature difference ΔT≈30 K, and (2) relatively low temperature ΔT≈330 K heat sources, for producing mechanical work, and thus electrical energy. The influence of three operating parameters, i.e., input heat flux, working fluid, and filling ratio, on the performance of the engine was characterized. Their optimum values, which yield... 

The effect of working fluid inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working fluid inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different...