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Waste Heat Recovery
Published in Stephen A. Roosa, Steve Doty, Wayne C. Turner, Energy Management Handbook, 2020
The earliest waste heat-recovery devices were called regenerators. These consisted of extensive brick work called checkerwork, located in the exhaust flues and inlet air flues of high-temperature furnaces in the steel industry. Regenerators are still used to a limited extent in open hearth furnaces and other high-temperature furnaces combusting low-grade fuels. It is impossible to achieve steel melt temperature with the fuels used unless regenerators are used to boost the inlet air temperature. In this process, vast amounts of waste heat are recovered which would otherwise be supplied by expensive high-Btu fuels. Pairs of regenerators are used alternately to store waste heat from the furnace exhaust gases and then transfer that heat to the inlet combustion air. The transfer of exhaust-gas and combustion-air streams from one regenerator to the other is accomplished by using a four-way flapper valve. The design and estimates of the performance of recuperators follows the principles presented in section 8.4. One disadvantage of this mode of operation is that heat-exchanger effectiveness is maximum only at the beginning of each heating and cooling cycle and is ineffective at the end of the cycle. A second disadvantage is that the large mass of the checkerwork and the volume required for its installation raises capital costs above that for the continuous-type air preheaters.
System Selection and Optimization
Published in Samuel C. Sugarman, HVAC Fundamentals, 2020
A heat exchanger is a device specifically designed to transfer heat between two physically separated fluids. The term heat exchanger can describe any heat transfer device such as a coil or a particular category of devices. Heat exchangers are made in various sizes and types. The basic types of heat exchangers are shell and tube, shell and coil, U-tube, helical, and plate. Typical HVAC heat exchangers are designed for a number of fluid combinations including steam to water (converter), water to steam (generator), refrigerant to water (condenser), water to refrigerant (chiller), water to water (heat exchanger), air to refrigerant (coil), and air to water or water to air (coil).
Basic Design Methods of Heat Exchangers
Published in Sadık Kakaç, Hongtan Liu, Anchasa Pramuanjaroenkij, Heat Exchangers, 2020
Sadık Kakaç, Hongtan Liu, Anchasa Pramuanjaroenkij
The flow chart of heat exchanger design methodology is given in Figure 2.17.15 The first criterion that a heat exchanger should satisfy is the fulfillment of the process requirements: the design specifications may contain all the necessary detailed information on flow rates of streams, operating pressures, pressure drop limitations for both streams, temperatures, size, length, and other design constraints such as cost, type of materials, heat exchanger type, and arrangements. The heat exchanger designer provides missing information based on his/her experiences, judgment, and the requirements of the customer.
A practical approach-based technical review on effective utilization of exhaust waste heat from combustion engines
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Rajesh Ravi, Oumaima Douadi, Manoranjitham Ezhilchandran, Mustapha Faqir, Elhachmi Essadiqi, Merouan Belkasmi, Shivaprasad K. Vijayalakshmi
The recuperated thermal energy can be used to generate additional electricity or to operate the chillers in Stirling engines or ORC systems for cooling purposes (Weiland Christoph et al. 2023). The addition of a Hex can boost the system’s total efficiency from 30% (power alone) to around 60% (cogeneration power). Figures 13 and 14 depict heat recovery modes and various heat exchangers (Hex), respectively. The recovery of waste heat from the remaining engine components can increase efficiency by up to 80% (Rodriguez 1997). However, determining the quantity of exhaust heat recovered is critical since the exhaust gas temperature must not go below 120°C in order to prevent condensation in the heat exchanger (Hijriawan et al. 2022). Temperature sensors are required for both the Hex and the engine in order for autonomous engine shutdown technology to work (Huikun Cai et al. 2019). In the case of a gas circuit failure, the water circuit must be temporarily used to disperse remaining heat from the Hex (Abdelkareem et al. 2022). Heat exchangers are extremely efficient and help with energy recovery, resulting in considerable cost and resource savings (Christodoulides Paul et al. 2022).
CFD study on heat transfer and pressure drop of nanofluids (SiO2/H2O, Al2O3/H2O, CNTs/H2O) in a concentric tube heat exchanger
Published in International Journal of Ambient Energy, 2022
Ankit Kumar Gupta, Bhupendra Gupta, Jyoti Bhalavi, Prashant Baredar, Hemant Parmar, Ramalingam Senthil
Day by day, the energy consumption increases, so the fulfilment of the energy demand of everyone around the world has become one of the biggest challenges. Researchers, scientist and engineers try their best to develop methods and devices which decrease the energy wastages and give optimum utilisation of available energy. Many devices are used in industries, power plants, refrigeration, air conditioning, automobiles, transportation and machining operation, with tremendous potential for energy conservation. One of those devices is the heat exchanger, so the importance of heat exchanger from the viewpoint of energy conservation increases immensely. A heat exchanger is a device that is used for heat transfer between hot fluids and cold fluids. There are several types of heat exchanger such as shell and tube heat exchanger, plate heat exchanger, helical coiled heat exchanger, radiator, double-pipe heat exchanger, micro heat exchanger, cooling tower and compact heat exchanger are presently used in various applications. Most of the heat exchangers are of the indirect contact type heat exchanger in which cold and hot fluid are separated from a wall and heat from hot fluids to cold fluids is transferred from the wall.
Heat Transfer Characteristics of Plate Heat Exchanger with Bubble Fin Using Al2O3/Water Nanofluid: Numerical Investigation
Published in Heat Transfer Engineering, 2022
Sandeep Kumar, Sudhir Kumar Singh, Deepak Sharma
A heat exchanger is a device adapted to perform exchange of heat from one fluid to another fluid according to need as heating or cooling. Heat exchangers having gaskets are used in low or medium pressure applications, whereas brazed and welded plates are used for high pressure applications [1]. The different working fluids used for single-phase and two-phase flow heat transfer in heat exchanger equipments are water, air, ethylene-glycol, nanofluids (oxide-based, carbon-based, hybrid), refrigerants, etc. The use of nanofluids in plate heat exchanger (PHE) is the area of research due to their higher heat conduction rate and stability, lower chances of erosion, clogging, and pumping power. [2]. PHEs have been extensively used in energy transfer applications such as milk pasteurization units, pharmaceutical industries, refrigeration units in chemical industries, for their greater efficiency and compact structure [3]. Due to high pressure drop in corrugated PHEs, the situation appeared for modification in design of PHE.