Experimental investigation on thermal performance of cavity receiver integrated with short-term thermal energy storage f
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Experimental investigation on thermal performance of cavity receiver integrated with short‑term thermal energy storage for a solar parabolic dish concentrator V. Thirunavukkarasu1 · Vivek U. Nair1 · Kunal Tiwari1 · M. Cheralathan1 Received: 12 June 2020 / Accepted: 26 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Solar parabolic dish collectors are widely used for solar thermal energy conversion for various medium- and high-temperature applications. One of the problems being faced by the receivers of parabolic dish collectors is the short-time non-availability of solar radiation because of cloud cover. This affects the useful output and also results in a sudden change in the receiver temperature, which induces thermal stress in it. Hence receiver with short-term thermal energy storage is attempted to tackle this issue. A hemispherical cavity receiver is developed with a double-layered wall, and the space between the two layers is filled with a salt bath composed of a eutectic mixture of NaNO3 and KNO3 as phase change material. The heat transfer fluid flows through the copper tubes that are coiled in the gap between the two layers. The phase change material surrounds the copper tubes and acts as a storage as well as a heat transfer medium. Experimental results show that the integration of the storage medium to the receiver has a good impact on the thermal output, even during irregular radiation input conditions. The receiver has attained a net energy efficiency of 31.4% for an average irradiance of 561 Wm−2. Keywords Solar parabolic dish collector · Cavity receiver · Phase change material · Thermal energy storage · Thermal output · Efficiency Abbreviations Aap Effective aperture area of reflector dish (m2) Cp Specific heat capacity (kJ kg−1 K−1) Cpl Specific heat capacity of the material in the liquid state (kJ kg−1 K−1) Cps Specific heat capacity of the material in the solid state (kJ kg−1 K−1) Ib Solar beam radiation (Wm−2) ṁ Mass flow rate of heat transfer fluid (kg s−1) Ti Initial temperature of phase change material (K) Tf Final temperature of phase change material (K) Tm Melting point temperature of phase change material (K) Tin Inlet temperature of heat transfer fluid (K) Tout Outlet temperature of heat transfer fluid (K)
* V. Thirunavukkarasu [email protected] 1
Tt,i Initial temperature of heat transfer fluid in the storage tank (K) Tt,f Final temperature of heat transfer fluid in the storage tank (K) QD Concentrated solar radiation power or dish power (kW) QR Receiver power (kW) QS Solar radiation power on the reflector dish (kW) Qst Heat energy stored (kJ) l Receiver tube length (m) m Mass of heat transfer fluid (kg) mpcm Mass of phase change material (kg) n Day of the year t Time of operation of the system (s) 𝜂opt Combined optical efficiency of reflector dish (%) 𝜂net Net energy efficiency of the receiver (%) δi Solar declination angle HTF Heat transfer fluid LPM Litres per minute LH Latent heat
Department of Mechanical Engineering, SRM Ins
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