Showing papers by "Cyrus Aghanajafi published in 2021"

An experimental investigation of microstructure surface roughness on pool boiling characteristics of $${\mathrm{TiO}}_{2}$$ TiO 2 nanofluid

Abstract: An experimental setup for pool boiling of dilute dispersions of titanium dioxide (TiO2) nanoparticle in water-ethylene glycol 50 (WEG50) as the base fluid was developed. The nanofluid was stabilized by using sodium lauryl sulfate as a surfactant. The heater surface roughness was affected by the deposition of nanoparticles during boiling which consequently changes the heat transfer characteristics. Three copper heater surface roughnesses: smooth, semi-rough and rough, were used. The effect of surface roughness and nanofluid on boiling heat transfer coefficient (BHTC), surface wettability and nucleation site density were examined. The results showed that BHTC and nucleation site density were increased by increasing the heater surface roughness in the base fluid of WEG50. The findings of this study revealed that the effect of volume concentration of nanofluid on the BHTC significantly depends on the heater surface roughness. At heater surface roughness of 0.062 μm, BHTC increases compared to WEG50 base fluid for all volume concentrations of TiO2-WEG50 nanofluid. With increasing the volume concentration of nanofluid up to 0.005%, an increasing tendency in BHTC was observed but beyond that a decreasing trend was observed for heater surface roughness of 1.213 μm. However, as heater surface roughness reaches 3.146 μm, BHTC decreased by increasing nanofluid volume concentration, compared to WEG50 base fluid. Also, increment of heater surface roughness causes the nucleation site density to increase when either base fluid or nanofluid is used. By measuring static contact angle of sessile water droplet on heater surface before and after experiment, it was found that using TiO2-WEG50 nanofluid causes to surface wettability increased.

Analyzing the sensitivity and energy efficiency of a residential complex in warm and dry climate of Iran: the case study Yazd Province

Abstract: In recent years, the limited energy sources and their huge costs in many countries to save money have attracted the attention of many scholars. The purpose of the energy consumption assessment of a building is to reduce the waste of the energy, and this reduction in the energy has a direct relationship to the lower costs. In this paper, the researcher tends to investigate the sensitivity and the energy analysis of a warm and dry residential complex in Iran (Yazd). Initially, the simulation of the energy consumption of a building was calculated by using the eQUEST software, to determine the thermal load of the building for a range of important parameters (such as wall insulation, roof and floor insulation, air penetration, glass type and window size). Then by using the SPSS software, the relationships have been extracted to connect the energy of the building with these factors. Then, by using the SPSS software, it attempted to connect a meaningful relationship between the energy consumption of the building and the mentioned factors. Also, the energy efficiency of the building was optimized by converting the data to the neural network, by using the genetic algorithm. Finally, this study was also carried out in warm and dry areas, to describe the accuracy of the results, and in each step, appropriate validations have been done.

Optimization Techniques for Design a shell and tube heat exchanger from an economic viewpoint

Abstract: This paper aims to minimize the total annual cost for a shell and tube heat exchanger based on optimization algorithms. The total annual cost is the sum of the initial cost for the construction of the heat exchanger and the cost of power consumption in the shell and tube heat exchanger. The total annual cost is the objective function, which is minimized. This research uses three optimization algorithms including particle swarm optimization, genetic algorithm, and differential evolution, and three optimization variables including shell’s inside diameter, tubes’ outer diameter, and baffle spacing. Three different studies have been used to compare the results. The results demonstrated that the differential evolution algorithm achieved the most decline in the total annual cost compared to other optimization algorithms. Using differential evolution algorithm, the total annual cost was decreased about 30% in study 1 and about 28.1% in study 2 compared with literature, respectively. The reduction in the total operating cost is about 47.7% for differential evolution algorithm, 45.7% for particle swarm optimization, and 45.3% for genetic algorithm relative to the results reported in the literature for case study 3. Results were compared with at least eight works directly and have been demonstrated in this research.

Selection of prime mover to meet heating demand of a single effect absorption chiller based on laws of thermodynamics

Abstract: 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 mover capacity. The number of prime movers is estimated based on the required heating power of the generator steam for each partial load. It is seen, the entropy generation would be decreased rapidly by increasing the generator temperature and after a while, the entropy generation would be approximately constant. The optimum entropy generation for each condensing temperature and the generator temperature may be decreased by increasing the evaporator temperature. It is deduced that COP is increased rapidly by increasing the generator temperature but in the following, the COP will be constant. The maximum amount of COP is decreased by increasing the condensing temperature. Also the COP is increased by increasing evaporator temperature for a certain generator and condensing temperatures.

Numerical solution of coupled radiative and conductive heat transfer’s equations in PolyMethylMethAcrylate by the finite difference method

Abstract: This study has been conducted to illustrate combined heat transfer in a PolyMethylMethAcrylate (PMMA) sample. PMMA is a promising polymer utilized to optical, pneumatic actuation, sensor, analytica...