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The optimization of the heat recovery steam generator (HRSG) is one of the key elements for increasing the efficiency of combined plants. According to the current technical practice, it can be organized at different levels of complexity with objectives sequentially defined: operating parameters, geometrical details and technological elements.According to this point of view, in the paper a complete...
Many research and development projects throughout the world are devoted to sustainable hydrogen production processes. Low-temperature electrolysis, when consuming electricity produced without greenhouse gas emissions, is a sustainable process, though having limited efficiency.The performance of electrolysis processes can be improved by functioning at high temperature (high-temperature electrolysis,...
In this paper, exergy transfer effectiveness is defined to describe the performance of heat exchangers operating above/below the surrounding temperature with/without finite pressure drop. It is discussed systemically that the effects of heat transfer units number, the ratio of the heat capacity of cold fluids to that of hot fluids and flow patterns on exergy transfer effectiveness of heat exchangers...
Exergy change rate in an ideal gas flow or an incompressible flow can be divided into a thermal exergy change rate and a mechanical exergy loss rate. The mechanical exergy loss rates in the two flows were generalized using a pressure-drop factor. For heat exchangers using in waste heat recovery, the consumed mechanical exergy is usually more valuable than the recovered thermal exergy. A weighing factor...
In this paper, two desiccant-coated heat exchangers, which are actually fin-tube heat exchanging devices coated with silica gel and polymer materials respectively, are investigated experimentally. Due to the hygroscopic properties of the desiccant materials, both the sensible heat and the latent heat of the process air can be handled by using this kind of heat exchanger. An experimental setup was...
Building legislation along with environmental and comfort concerns are increasingly driving designers of building services and air conditioning equipment towards more energy efficient solutions. Heat pipe technology is emerging as a viable, efficient and environmentally-sound technology for applications in efficient air handling unit designs. In this paper, an experimental investigation on the thermal...
Taking into account inner and external multi-irreversibilities, a complete numerical model of commercial thermoelectric generator with finned heat exchangers is established by combining thermodynamics with heat transfer theory. A significant novelty is that physical properties, geometric dimensions, temperature parameters and flow parameters are all considered in the model. The inner effects include...
In this research, design factors for a heat exchanger and boiler were investigated using a simplified model of a heat exchanger and pilot condensing boiler, respectively. Specifications of each heat exchanger component (e.g., upper heat exchanger (UHE) and lower heat exchanger (LHE); coil heat exchanger (CHE); baffles) were investigated using a model apparatus, and the comprehensive performance of...
Exergy has proved to be a useful tool to analyze and optimize the design and operation of many systems. Some studies on helium refrigerators and liquefiers based on exergy are available in literature. In this paper, systematic evaluation of important operating and geometric parameters has been done to determine the exergy destructions in components as well as in the entire cycle of Collins helium...
In the 20th Century many buildings became totally dependent on fossil fuel energy to make them habitable. Recent legislation and building regulations, however, ensure that designers are contracted to aim for zero carbon sustainability or buildings which function with much lower levels of fossil fuel dependency.Heat pipe technology has found increasing applications in the building service industry...
Based on the entransy dissipation theory, the multi-parameter optimization design of recuperator is conducted in an Isopropanol–Acetone–Hydrogen (IAH) chemical heat pump system. The performance of the heat pump system can be improved significantly through the multi-parameter optimization, when the main operation parameters of chemical heat pump remain unchanged. When the main operation parameters...
The effect of the distance between the burner and the heat exchanger on the heat transfer characteristics and NO x and CO emission characteristics in a compact combustion system was studied. The premixed burner was installed in front of a heat exchanger, and the distance between the burner and the heat exchanger was varied from 30 mm to 50 mm to experimentally investigate the effect of distance...
In the present work, we focus on an incomplete combined heat and power (CHP) system. The supplementary thermal performance has been designed to increase the efficiency of the heating system by designing a shell and tube heat exchanger to recover the heat from the exhaust gases. A plate heat exchanger has also been designed for cooling the biogas-diesel generator and the exhaust gases. Two types of...
Heat removal systems are of primary importance in several industrial processes. As heat sink, a water pool or atmospheric air may be selected. The first solution takes advantage of high heat transfer coefficient with water but it requires active systems to maintain a constant water level; the second solution takes benefit from the unlimited heat removal capacity by air, but it requires a larger heat...
This study evaluates the vehicle exhaust WHR (waste heat recovery) potential using a RC (Rankine cycle ). To this end, both a RC thermodynamic model and a heat exchanger model have been developed. Both models use as input, experimental data obtained from a vehicle tested on a chassis dynamometer. The thermodynamic analysis was performed for water, R123 and R245fa and revealed the advantage of using...
The power generation of exhaust TEG (thermoelectric generator) depends on heat energy and thermoelectric conversion efficiency. High efficiency heat exchanger is necessary to increase the amount of heat energy extracted from exhaust gas. On one hand, heat transfer is coupled with pressure drop for typical heat exchanger; on the other hand, the muffler unavoidably leads exhaust to large pressure drop...
In this paper, the concept of entropy resistance is proposed based on the entropy generation analyses of heat transfer processes. It is shown that smaller entropy resistance leads to larger heat transfer rate with fixed thermodynamic force difference and smaller thermodynamic force difference with fixed heat transfer rate, respectively. For the discussed two-stream heat exchangers in which the heat...
An experimental investigation of the performance of a wraparound loop heat pipe (WLHP) charged with R134a is reported in this paper. The copper WLHP has a two-pass evaporator section and a two-pass condenser section, each pass is 330 mm in length with an inner tube diameter of 11.2 mm. The considered configuration is similar to that used to build industrial heat exchangers, which are used for heat...
This paper examines the advantages of using the ethanol–water azeotrope as a wickless heat pipe working fluid and the suitability of an inclined condenser structure for a horizontal evaporator operation. Water has, also, been tested as a working fluid for the heat pipe for comparison with the azeotrope results. The tested wickless heat pipe, or as sometimes is referred to as two-phase closed thermosyphon...
Curved pipes constitute essential components in engineering systems such as heat exchangers, and process pipelines. In curved pipes with 180° bends, the excess pressure drop, and the excess entropy generation (through heat and fluid flow) bring forth serious penalties. To overcome these difficulties a new partially curved pipe will be examined in this paper. It consists of three straight pipe segments...
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