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Energy: Storage
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Air Quality and Energy Systems, 2020
A regenerator is a regenerative heat exchanger, in which energy is stored in the material of the heat exchanger itself. A regenerator cycles such that half of it is heated by hot flue or exhaust gases while cool combustion air is drawn in and heated in the other half. In the second half of the cycle, cool air enters through the previously heated material of the regenerator. For example, older industrial furnaces have two chimneys, where combustion air enters in one while flue gases heat the other. Then the paths are switched so that new air is heated as it descends the first, heated chimney. A newer type of regenerator is a slowly rotating heat wheel, with half of it being heated by exiting flue gas and the other half heating the incoming air. The paths of the intake and exhaust remain constant while the heat-storing element moves.
Analysis of Thermal Energy Systems
Published in Steven G. Penoncello, Thermal Energy Systems, 2018
The combustion process is inherently irreversible. Research into new combustion methods may eventually result in reducing the exergy destruction in a combustion chamber. However, the improvement is likely to be small. The exergy destruction rate in the combustion process is something that engineers must accept. The largest waste of the exergy resource in the gas turbine system analyzed here is venting the hot combustion products to the atmosphere. There are many other uses for this wasted exergy and if they are implemented in a larger scheme (e.g., using the hot combustion gases to provide space heating and/or water heating), then the system must be expanded and analyzed to include the additional equipment. This will result in higher exergetic efficiency and a more favorable view of the system as whole. Another possibility is to redesign the gas turbine system itself and use the hot combustion gases to preheat the air entering the combustion chamber, as shown in Figure 3.23. The heat exchanger used to preheat the combustion air is known as a regenerator. The regenerator is an effective way to capture the otherwise lost exergy at the power turbine exhaust and transfer it back into the system resulting in higher thermal and exergetic efficiencies; a better use of the fuel’s exergy resource.
Generator Driver Applications and Selection
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
A regenerator, or recuperator, is a heat exchanger that transfers heat from turbine exhaust gas to compressor discharge air prior to fuel combustion, displacing a portion of fuel heat input that would otherwise be required. Unit capacity (as a result of heat exchanger pressure drops) is usually decreased somewhat, but cycle thermal fuel efficiency is increased. Reduced exhaust temperatures limit the quality and quantity potential for exhaust gas heat recovery.
Theoretical analysis on pressure drop across porous cryocooler regenerator in evaluating the optimum regenerator porosity
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
K. V. Srinivasan, A. Manimaran, M. Arulprakasajothi, Rahul D. Pokale, Vijay A. Arolkar
The matrix geometry of an efficient regenerator must possess the following characteristics such as infinite heat transfer area, negligible axial conduction, negligible pressure drop, reduced void volume, etc. The porosity requirement dictates the size of the regenerator. The area of the regenerator matrix has to be large to improve its heat transfer rate and thereby reducing the temperature difference between gas and matrix. However, a large regenerator may also have a large void volume (Bhadarka and Dayal 2015). The large void volume is reduced by using a fine structure, but at the cost of higher frictional pressure drop between gas and matrix. List of common regenerator geometries mentioned in Figure 1. The wire mesh is commonly used as the matrix material (Figure 1b), which offers high heat transfer area with lower entropy generation rate (Ackermann 1997).
Experimental Study on Effectiveness of Celdek Packed Liquid Desiccant Cooling System
Published in Heat Transfer Engineering, 2018
Rakesh Kumar, Arun Kumar Asati
The effect of inlet process parameters on the effectiveness of a structured packed dehumidifier and regenerator using calcium chloride as desiccant is investigated experimentally with counter flow of the solution and air. The effectiveness of dehumidifier is observed to be increased with increasing mass flow rate of desiccant solution and inlet specific humidity of the air while it is found to be decreased with increasing inlet solution temperature, air flow rate and inlet temperature of the air. The effectiveness of regenerator increases with increasing solution flow rate and inlet desiccant concentration and it decreases with increasing inlet air temperature, air flow rate and inlet solution temperature. The effectiveness of the regenerator remains unaffected with varying inlet specific humidity of the air.
Investigate the effect of regenerator mesh on cooling performance
Published in International Journal of Ambient Energy, 2022
Fayaz H. Kharadi, A. Karthikeyan, Bhojwani Virendra, Asif Inamdar
A regenerator is a thermal storage material that periodically absorbs energy when exposed to a hot fluid and releases it to the same fluid at a later stage in a cycle. Thermodynamic cycles include regenerative heat transfer via a regenerator, in order to attain low temperatures and high performance. The regenerator is one of the key components of the regenerative cryocooler. Regenerator loss caused by the defects in the regenerative matrix and its structure account for a considerable proportion of the total losses. The regenerator used in these cycles has a flow conduit that is filled with a porous matrix having high surface area and heat capacity leading to large heat transfers. The hot fluid entering at a constant temperature heats the matrix for half of the cycle, and the cold fluid cools the matrix for the second half of the cycle while flowing in the reverse direction, thus periodically heating and cooling the matrix while reversing the flow. Robert Stirling (Ackerman 1997) used regenerator mesh in his first hot air engine (regenerative heat exchangers) to achieve low temperatures in Cryogenic Refrigerators or Cryocooler. The performance of regenerator mesh directly affects the Cryocooler Performance. To minimise the losses in regenerator mesh, three parameters should be changed i.e. size, material and packing geometry. The efficiency of the regenerator is largely dependent upon the ratio of the volumetric specific heat capacity of the regenerator matrix to that of helium. The regenerator matrix should have maximum heat transfer capacity, minimum flow loss and less contamination as it directly comes in contact with the working fluid (in this case helium gas). To serve these purposes, the porosity of matrix plays an important role. The matrix should be finely divided into the displacer tube. There should not any obstruction in the matrix during mass flow. Table 1 shows the requirements of a good regenerator (Jayaraman 2017).