REGENERATOR& RECUPERATOR Presented by: Animesh Saha Kabyashree Bora Shuvanando Das Deepjyoti Das Himangshu Deori MEB11019 MEB11021 MEB11022 MEB11023 MEB11027 INTRODUCTION • A heat exchanger is a device that is used to transfer thermal energy between two or more fluids, between a solid surface and a fluid or between solid particulates and a fluid at different temperatures and in thermal contact. • Usually, there is no external heat and work interactions. CLASSIFICATION Heat exchangers can be classified on the basis of... NATURE OF HEAT EXCHANGE PROCESS REGENERATOR RECUPERATOR DIRECT CONTACT RELATIVE DIRECTION OF MOTION OF FLUID CO-CURRENT OR PARALLEL FLOW CROSS-FLOW COUNTER-CURRENT OR COUNTER FLOW . MECHANICAL DESIGN OF HEAT EXCHANGE SURFACE MULTIPLE SHELL AND TUBE PASSES CONCENTRIC TUBES SHELL AND TUBE . Applications . low effective thermal heat conductivity in the longitudinal (gas flow) direction.gas turbines. open hearth and glass melting furnaces.high volumetric heat capacity.etc. The heat thus stored is subsequently transferred to the cold fluid by allowing it to pass over the hot matrix. . The heat is transferred to the solid matrix and accumulates there. Desired material properties . the operation is called heating period. The hot fluid is passes through a certain medium called matrix.REGENERATOR Storage type heat exchanger. Used when mixing of the two fluids is undesirable. . superheaters. oil heaters for an airplane. automobile radiators.RECUPERATORS Fluids flow simultaneously on either side of a separating wall. heat transfer occurs between the fluid streams without mixing or physical contact with each other.boilers. Applications .etc. The use of regenerator has been widespread for recovering heat from exhaust gases and preheating inlet air in commercial and residential oil-and coal-fired furnaces. because of the enormous heat-transfer required. or impractical. due to the likelihood of surface fouling by particulate matters. [4] .REGENERATOR Heat regenerator are often employed when the use of heat recuperators is either uneconomical. This heating period is followed by flow of cold gases over the hot solids i. [4] Fig: Rotary-bed regenerator [9] . Hot gas flows past the solids..Principles of Operation Heat is not exchanged directly between hot and cold fluids across a separation solid wall. A regenerator typically operates cyclically. it heats them while being cooled.e. Hot and cold gas flow alternately over solids with high heat capacity per unit volume that periodically absorb and release heat. the cooling period . for the other use. While hot gas passes into one. For continuous heating and cooling. The alternative is to rotate the solids between the hot and cold gas streams. as is done in a rotary (Ljungstrom) regenerator. This is called swing operation. Heat regenerators can be used either continuously to heat a cold gas and recover heat from a hot one. cold gas flows through the other. or to store thermal energy for use later on. the job is to find the fraction of energy that has been stored (heat storage factor) and predict heat leaks during storage. the main task is to ensure maximum energy recovery (the best thermal efficiency). and gas flows are switched at appropriate times. For continuous operation. two or more regenerators are used in parallel. [4] [10] Fig : Fixed-bed swing regenerator . Thermal Efficiency (1) [4] . [4] . [4] . [4] . The regenerator is placed between the air compressor and the combustion chamber.ANALYSIS OF THE FUNCTION OF REGENERATOR IN A GAS TURBINE POWER PLANT Flue gas coming out of gas turbine is fed into a regenerator. The regenerator pre heats the compressed air going into the combustion chamber. This reduces the heat input required thus increasing the efficiency of the power plant. . ANALYSIS OF THE FUNCTION OF A REGENERATOR IN A STEAM TURBINE POWER PLANT Steam coming out of the steam turbine is bled to the liquid before entering the boiler. the efficiency of the power plant increases. Thus. . The steam pre heats the air thus reducing the heat input to convert the liquid to steam. TYPES OF REGENERATOR FIXED BED REGENERATORS ROTARY REGENERATORS ROTHEMULE REGENERATORS . FIXED BED REGENERATOR Fixed bed regenerators use two or more regenerators operating out of phase with respect to one another so that while one regenerator is supplying heated fluid. . so another set open. at a reversal. the other regenerator(s) is storing heat from the heating fluid. when the cold fluid is drawn in. when one regenerator draws in heating fluid. As one set of valves close. Hence . the regenerator draws heat from the already heated regenerator and heats the cold fluid. the valves of the other regenerator is closed and the heat of the heating fluid is stored in the regenerator. In the next cycle. ROTARY REGENERATOR In a rotary regenerator. a porous packing is rotated around an axis. it stores heat. In its simplest form. as in the hot period of a fixed bed regenerator. This thermal energy is literally transported into the cold gas stream as the packing is rotated . the packing is divided into two gas tight sections and the hot and cold gases flow simultaneously in a direction parallel to this axis. As the packing rotates through the hot gas stream. The heat absorbing element in this type of regenerative air preheater is stationary rather than rotating. The hot flue gas enters at the top of the preheater and flows down through those exposed sections of the stationary heatabsorbing element that are not blocked by the rotating air outlet ducts. the air ducts in the preheater are rotated so as to alternately expose sections of the heating absorbing element to the up flowing air. thus heating those sections of the stationary element .ROTHEMULE REGENERATOR It is also known as stationary plate regenerator. Instead. . which however can be reduced to less than a per mille by using material with low heat conductivity like plastics. when the mixing is undesirable. or in the exhaust gases of an industrial process. [5] Description : It is the most important type of heat exchanger in which the flowing fluids exchanging heat are on either side of dividing wall (in the form of pipes or tubes generally). In a recuperator the only fundamental loss is the heat conduction through the wall in the flow direction. in order to recover the waste heat.e.What is Recuperator ? Defn A Recuperator is a type of counter-flow energy recovery heat exchanger positioned within the supply and exhaust air streams of an air handling system. [5] Fig.1 Types of recuperator profile [5] . These heat exchangers are used when two fluids cannot be allowed to mix i. 2 Recuperator in gas turbine engine [6] . [5] Fig.Recuperator in gas turbine engine Air is compressed. which is then burned and used to drive a turbine. The recuperator transfers some of the waste heat in the exhaust to the compressed air. thus preheating it before entering the fuel burner stage Since the gases have been pre-heated. mixed with fuel. the recuperator can make a heat engine or gas turbine significantly more efficient. less fuel is needed to heat the gases up to the turbine inlet temperature By recovering some of the energy usually lost as waste heat. alternate pairs of which are enclosed on two sides to form twin sets of ducts at right angles to each other. stainless steel. plastic. and into the supply air stream Recuperator selected for a pressure drop of between 150 and 250Pa will have a good efficiency [5] . or synthetic fibre. and which contain the supply and extract air streams. In this manner heat from the exhaust air stream is transferred through the separating plates.Recuperator in HVAC systems Recuperators are commonly used to re-use waste heat from exhaust air normally expelled to atmosphere Devices typically comprises a series of parallel plates of aluminium. have the most to gain from the use of a recuperator. In practice. [5] Fig. The larger the temperature difference between turbine out and compressor out.4 Recuperated Microturbine [8] . which typically have low pressure ratios. the greater the benefit from the recuperator. Therefore. a doubling of efficiency is possible through the use of a recuperator. reducing the fuel input required. The exhaust heat from the turbine is used to pre-heat the air from the compressor before further heating in the combustor. microturbine (<1MW).Recuperator in Microturbine Recuperator can be used to increase the efficiency of gas turbines for power generation. provided the exhaust gas is hotter than the compressor outlet temperature. 3 Air-to-Air Heat Recuperator set-up [1] . [1] Fig. [1] This surface is formed as a number of tubes. In principle. It is also possible to use the recuperated heat to heat water for cleaning purposes or air for heating rooms. there are two different recuperating systems: 1) Air-to-Air 2) Air-Liquid-Air [1] Air-to-Air Heat Recuperator In Air-to-Air Heat Recupeartor as shown in the figure.Heat Recuperator The main aim is to transfer the heat contained in the dryer exhaust air to preheat the drying air. inside of which the outgoing warm air is passing while the cold air is passing on the outside. the drying air is preheated by means of the outgoing air passing counter-currently over the heat surface of the recuperator. it may be expected that the temperature of the water gets below zero. As the heat transfer coefficient is higher for Air-Liquid than for Air-Air. Air-Liquid-Air Heat Recuperator More flexible regarding the installation Divided into two heat exchangers. this system is more efficient than the Air-to-Air heat recuperator despite the fact that two heat surfaces are needed. due to low air temperature during winter. in between which a heat transfer liquid is circulated If. an anti-freeze agent is added to the water. [1] Fig.4 Air-Liquid-Air heat recuperator set-up [1] . Classification of recuperators Recuperators Ceramic Conventional Recuperative burner Radiation Convection Combined . .Convection recuperator Convection recuperators are generally deployed with flue gases having temperatures 7001100°C.They utilize convection heat transfer to preheat combustion air or gas for the purpose of saving fuel. Radiation recuperatorsThe design of radiation recuperators is based on the thermal radiation of non-luminous gases contained in the products of combustion. and combustion air preheat temperatures are usually in the 426°C to 760°C range. . Waste gas temperatures entering radiation recuperators are usually in the 1090°C to 1371°C range. Combined recuperators When the flue gas temperature gets below 600650°C the emission from the gas becomes so weak that the heating surface is not used economically. One consequent solution is to introduce convection sections after the radiation recuperator. . Double recuperators available for efficiency up to 90% . 6. Aluminium and resistant to corrosion. No leakage between airflows. Very reliable & low maintenance. Passive heat recovery unlike rotating wheels 2. 4.Advantages of recuperators 1. Suitable in high humidity environments 5. 3. 2. Single recuperator efficienciy tends to be slightly lower than aheivable than wheels. Supply and exhaust airflows have to be adjacent. . No transfer of moisture.Limitations 1. which can also be an advantage ie pools 3. Retrieved March 20.A (1992).K. March 18). In Wikipedia. Theermopedia. Ramachandran.K. 2015 from http://www. . 2015 from http://en.P. WBDG. Basic and Applied Thermodynamics. 2015 from http://www. In Wikipedia. R. (2010).com/ [10] Fixed bed regenerator. The Free Encyclopedia.alentecinc. Retrieved March 20.org/resources/microturbines.wbdg.References [1] Çengel. Retrieved March 19.com/content/1087/ . Retrieved March 19. February 17). P. New Delhi: S. Heat Regenerators: Design and Evaluation [5] Recuperator. Boles. Retrieved March 19.industrialheating. Industrial Heating. P.htm [7] Regenerator.wikipedia.thermopedia. (2015.Chand & company Pvt. (2015. ALENTEC. Retrieved March 19. M.wikipedia. Michael (1994). (2014).. Yunus A. New Delhi: Tata McGraw Hill [4] Dudokovic. Heat and Mass transfer. 2015 from http://en. Ltd [3] Nag..org/wiki/Recuperator [8] Recupearted Microturbine.php [9] Fluid bed regenerator. 2015 from http://www. 2015 from http://www.. The Free Encyclopedia.com/power.org/wiki/Recuperator [6] Recuperated Gas turbine. Thermodynamics: An Engineering Approach [2] Rajput.