Nowadays solar still is widely used in solar desalination processes. This work presents a modified stepped solar still with 7 steps 35 mm high, 80 mm wide and 600 mm long and external Condenser. Phase Change Material is used as a heat storage source to continue to sweeten saline water after sunset. In this study, stearic acid has been used as phase change material. In order to increase the efficiency of the still, a fan has been used to suck the air in the stepped solar still and transfer it to the Condenser. The experiment was carried out in four modes: the first mode was simple, the second mode was only with the fan and the Condenser, the third mode, with stearic acid as phase change material, and the fourth mode was used simultaneously with the PCM and external Condenser. The results show that the maximum productivity was obtained in fourth mode of experiment which is increased 104%.

Cupronickel 90-10 is one of the most applicable Cu-based alloys which possess suitable corrosion resistance and strength and is employed extensively in marine industries particularly in the boilers and heat exchangers. Generally, the tubes of water cooling systems especially those use seawater as cooling medium are made of this alloy. In this paper, the causes of premature failure of a cupronickel (90-10) Condenser tube used in a cooling system of an oil refinery in the south of Iran have been studied by different microscopical and analytical methods, e.g. X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The results showed that pitting corrosion on the internal surface of the tube was the main cause of its failure which was a consequence of the stagnant of the tube by external solids and preparation of an appropriate environment for the activity of microorganisms, hence, microbial corrosion.

This paper proposes an approach for improving the plant efficiency by reducing the heat rejection temperature of power cycle using Kalina Cycle System 11 (KCS11) which is integrated at the steam Condenser of a 500 MWe SubC (subcritical) coal-fired power plant. It is modelled by using power plant simulation software ‘ Cycle Tempo’ at different plant operating conditions. Results show that the additional net electric power of 5. 14 MWe from KCS11 improves the net energy and exergy efficiencies of the power plant by about 0. 302 % point and 0. 27 % point, respectively at full load over the stand-alone coal-fired steam power plant. Thereby, the carbon dioxide (CO2) emission is reduced by about 2. 02 t/h at full load. Combined plant efficiencies decrease with decrease in evaporator outlet temperature due to decrease in vapour quality of binary mixture at turbine inlet and higher steam turbine back pressure. Levelized Cost of Electricity (LCoE) generation and payback period of the combined cycle power plant are about Rs 1. 734 and 4. 237 years, respectively and the cost of fuel saving is about Rs 0. 685 per kg of coal which is lower than the fuel cost.

There is a demand for reduced power consumption in the vapor compression refrigeration cycle. Coefficient of performance of window-air conditioners considerably decreases and power consumption increases under very hot conditions.These problems have encouragecl studies aimed at improving the performance of window-air-conditioners by enhancing the heat transfer rate in the Condenser. In this article, a new design for application of evaporative cooling in the Condenser of window-air conditioners is introduced and experimentally investigated. In this design, two pads equipped with a water injection system are located on both sides of the air-conditioner to cool down the air flow passing over the Condenser. The experimental results showed that thermodynamic characteristics of the system considerably improved while power consumption decreased by about 15% and the coefficient of performance increased by about 55%.

In the present work, heat transfer augmentation during condensation of R-134a vapors inside horizontal twisted tapes inserted tubes has been investigated experimentally. Test Condenser was a double pipe counter flow water cooled heat exchanger which refrigerant flowed inside the internal tube, while water flowed in the annulus. Twisted tapes with different twisted ratios were used in full length of test Condenser. It is found that the use of twisted tape increased the condensing heat transfer rates by as much as 43 percent above the plain tube values on a nominal area basis. Influence of a variety of parameters such as vapor quality and twisted  tape geometry on the heat transfer augmentation was also investigated. An empirical correlation was developed to predict the enhanced heat transfer coefficients.

A triple-tube heat exchanger composed of a Condenser and evaporator was proposed in this study. Also, the heat exchanger is partly filled with metal foam for improving performance. So that in addition to heat transfer enhancement, the pressure drop does not exceed the value expected by the designer. A system of six differential equations is formed under the coupled interfacial boundary conditions,accordingly, the dimensionless relations of velocity and temperature for fluid and solid are analytically obtained using continuity, momentum, and energy equations in porous and clear regions. In the solution method, first by normalizing, linear combination, and the variable change method, the differential equations are decoupled, and then by forming the Bessel differential equations, the solutions are obtained in terms of the modified Bessel functions of the first and second kind. In the porous medium, the local thermal non-equilibrium and the Darcy-Brinkman models are used in the energy and momentum equations, respectively. Also, to validate the analytical solutions, numerical simulation using Ansys-Fluent software with UDF coding was employed. The results showed that at high values of pore density, the effect of porosity on pressure drop is relatively small. The porosity 0. 97 as the optimum performance point and the dimensionless porosity radius 1. 78 as the critical hydraulically point was obtained. One of the most important results of this research is that the performance of the partly porous triple-tube heat exchanger improves significantly nearly three times compared to the non-porous one.

Improving the performance of solar heat pumps has always been of interest to researchers. The purpose of this study has been to find the optimal state of carbon nanotube (CNT) concentration in the refrigerants and Condenser copper tubes as well as the total tube length and the diameter of the Condenser helical coil, in order to maximize the exergy and heat transfer. The investigation has been carried out by the numerical method using finite volume, unsteady and laminar flow. The genetic algorithm has been used to obtain the optimum choice for the Condenser in two states of constant and variable diameter. Three concentrations of 0, 0. 5 and 1 percent for the carbon nanotubes in the refrigerant, three concentrations of 0, 1 and 3 percent for the carbon nanotubes in the copper tube, three different values for the Condenser diameter in each of the two states of constant and variable diameter, and three different Condenser tube lengths have been investigated. The results show that the use of CNT in the refrigerant, always increases the Nusselt number and the exergy while, the use of CNT in the wall structure of the Condenser copper tube reduces them. The results also show that the use of carbon nanotubes in the refrigerant increases the Nusselt number by 16% to 21%, and the exergy by 9% to 13%. However, using carbon nanotubes in the Condenser copper tube wall reduces the Nusselt number and the exergy up to 9. 5% and 18% respectively.

In this paper, the application of evaporative cooling for refrigeration cycle to reduce power consumption in hot climates is emphasized Experimental and analytical investigations were performed in order to specify the effect of evaporative cooling Condenser instead of the commonly used air cooling Condenser in window-air-conditioners. Evaporative Condenser can reject more heat, thereby preventing the reduction of cooling capacity and increasing power consumption of window-air-conditioners during very hot seasons. Two designs were developed for evaporative Condensers. In the direct injection design, water is injected on the Condenser coil directly while in the media pad design, water is injected on the media pad installed before the Condenser. Thermodynamic properties of the systems after modification were measured and compared with the ordinary situation. Analysis of the results show that using these methods, the coefficient of performance increases by about 25% and power consumption decreases by about 13%. It is also anticipated that further modifications in these designs may yield better results.

Conservation of energy by waste heat recovery is important not only for cost reasons, but also for reducing primary energy consumption as well as reducing carbon dioxide production. This paper explains and discusses the simulation, performance, and successful applications of thermosyphon heat exchangers (THE’s) for recovering waste heat from exhaust gases in industrial plants. The advantages of this system are compactness, flexibility of system size, ease of operation, and minimum maintenance requirements. The thermosyphon heat exchanger can satisfactorily act as a pre-heater of air in boilers and furnaces using the heat recovered from the exhaust. In this work, one successful industrial practice is explained using thermosyphon heat exchanger. The THE was simulated to recover waste heat from the exhaust of a nearly 7 ton boiler in the SAMEN company. The energy recovered from the flue gas is used to preheat the incoming air to the boiler. The average rate of waste heat recovery and thermal effectiveness obtained from computer simulation are 100 kW and 40%, respectively. The payback period was less than two years. The evaluation of the thermal performance of the THE was based on the effectiveness-NTU and LMTD methods to obtain the heat transfer characteristics.