Thermal and economic analysis of plastic heat exchangers for solar water heating
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The feasibility of polymer heat exchangers for solar water heaters is examined in terms of thermal performance and cost of tube-in-shell and immersed designs. High temperature nylon and cross-linked polyethylene were identified as suitable polymers for this application. These materials can meet the high temperature and pressure requirements of a domestic potable hot water system. The heat exchanger designs are compared for heat transfer area required to provide 3,000 and 6,000 W. A nylon tube-in-shell heat exchanger, sized for a 3,000 W load, is approximately 80% of the cost of a copper tube-in-shell heat exchanger. For an immersed heat exchanger, a high temperature nylon tube bank design has the lowest cost. The nylon tube bank heat exchanger, sized for a 3,000 W load, is approximately 80% the cost of an immersed coiled copper tube heat exchanger.Cite
Highly compact flat-tube, multi-louvered surface heat exchangers are being used to replace conventional round-tube/flatplate fin geometries in automotive engine cooling and air-conditioning systems. These novel heat exchangers can benefit absorption systems, which are gaining increased attention as an environmentally friendly replacement for the CFC-based vapor compression cycles that are used in residential and commercial air-conditioning. A study of condensation of ammonia in air-cooled heat exchangers was conducted. Two-phase flow, heat-transfer and pressure drop in the novel flat tubes were modeled by adapting the available literature on round tubes. A computer program that enabled the detailed design of these heat exchangers was developed. A systematic study of the effect of all geometric parameters on heat exchanger size was conducted. The analysis showed that the flat-tube, multi-louvered fin heat exchanger geometry offers the design flexibility to change many geometric variables to achieve the desired heat duty and tube-side and air-side pressure drops. Tube and fin depth, and fin spacing were found to have a significant effect on the required heat exchanger mass. Louver geometry may be used to further refine heat exchanger designs. It was also shown that the available air flow rate has a very significant effect on heat exchanger performance.more » A decrease in air flow rate of just twenty percent could increase the heat exchanger mass requirements by a factor of 1.6.« less
Louver
Fin
Recuperator
NTU method
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Covers practically the whole gamut of practical methods of design in almost every facet of heat transfer situations. Each section is prepared by a world expert in that particular area in such a manner as to be readily understood and applied. Following a detailed discussion of the basic principles an
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Thermosiphon
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Solar gain
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Due to the increased power cost and in the direction of using sustainable power sources, an emblem new environmentally high-quality water heat exchanger format is furnished in this article. This heat exchanger has been implemented thru using refurbished radiators from window-type air conditions. Two radiators are blanketed with ash particles depositing fouling on super-heated tubes to increase solar irradiation absorption. Temperature readings from inside the water inlet and outlet of the tool were recorded. Newton’s second law method is used to calculate the thermal power received thru water and the system's overall performance all through the period from 8:30 AM to 2:30 PM. The most recorded water temperatures and efficiencies for the primary and the second exchanger were (54.3 °C, 47%), (56.7 °C, 49%), respectively. The results show a comprehensive performance of a heat exchanger that has been modified as a solar heat storage to work as a solar water heater at a lower cost.
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Heat exchanger is a device used to accomplish the transfer of heat from one fluid to another. There are a wide variety of applications regarding shell and tube heat exchangers in the fields of petroleum and industrial applications, due to its enhanced heat transfer characteristics. This project was designed to establish an insight of detailed design and performance of the shell and tube heat exchanger based on energy and mass conservation laws. Solar water heating system techniques were used to provide the system with necessary hot water. One of these techniques was to evacuate tube solar heating system which can be considered as a more efficient way to supply this system with hot water. To enhance the system performance, proper material selection for shell and tubes structure and flow pipe network based on their availability in the local markets was brought into consideration as well. Furthermore, the implemented design was examined under Medina climatic conditions for its cost-effectiveness, simplicity, execution and sustainability. It was found that the heat exchanger efficacy, performance and the vacuum tube efficiency were in highly acceptable ranges and cost effective. In addition, the vacuum tube solar water heating was found to be a clean and safe source of renewable energy. Finally, a comprehensive analysis of the system effectiveness was conducted and the outlet temperature determined for the system varied between 44 to 50ºC for the heat exchanger whereas the vacuum tube exit temperature was elevated up to 84 to 90ºC. The efficiency of the solar collector was found to be 61.84%.
Thermosiphon
Solar water heating
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The compression process necessary for the liquefaction of natural gas on offshore platforms generates large amounts of heat, usually dissipated via sea water cooled plate heat exchangers. To date, the corrosive nature of sea water has mandated the use of metals, such as titanium, as heat exchanger materials, which are costly in terms of life cycle energy expenditure. This study investigates the potential of a commercially available, thermally conductive polymer material, filled with carbon fibers to enhance thermal conductivity by an order of magnitude or more. The thermofluid characteristics of a prototype polymer seawater-methane heat exchanger that could be used in the liquefaction of natural gas on offshore platforms are evaluated based on the total coefficient of performance (COPT), which incorporates the energy required to manufacture a heat exchanger along with the pumping power expended over the lifetime of the heat exchanger, and compared with those of conventional heat exchangers made of metallic materials. The heat exchanger fabricated from a low energy, low thermal conductivity polymer is found to perform as well as, or better than, exchangers fabricated from conventional materials, over its full lifecycle. The analysis suggests that a COPT nearly double that of aluminum, and more than ten times that of titanium, could be achieved. Of the total lifetime energy use, 70% occurs in manufacturing for a thermally enhanced polymer heat exchanger compared with 97% and 85% for titanium and aluminum heat exchangers, respectively. The study demonstrates the potential of thermally enhanced polymer heat exchangers over conventional ones in terms of thermal performance and life cycle energy expenditure.
Thermal energy
Liquefied natural gas
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The application of the thermoelectric generator (TEG) system to various industrial facilities has been explored to reduce greenhouse gas emissions and improve the efficiency of such industrial facilities. In this study, numerical analysis was conducted according to the types and geometry of heat exchangers and manufacture process conditions to recover waste heat from a billet casting process using the TEG system. The total heat absorption increased by up to 10.0% depending on the geometry of the heat exchanger. Under natural convection conditions, the total heat absorption increased by up to 45.5%. As the minimum temperature increased, the effective area increased by five times. When a copper heat exchanger of direct conduction type was used, the difference between the maximum and minimum temperatures was significantly reduced compared to when a stainless steel heat exchanger was used. This confirmed that the copper heat exchanger is more favorable for securing a uniform heat exchanger temperature. A prototype TEG system, including a thermosyphon heat exchanger, was installed and a maximum power of 8.0 W and power density of 740 W/m2 was achieved at a hot side temperature of 130 °C. The results suggest the possibility of recovering waste heat from billet casting processes.
Thermosiphon
Recuperator
Thermoelectric generator
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