Accepted Manuscripts

Su Guo, Yinghao Chu, Deyou Liu, Xingying Chen, Chang Xu, Carlos F. M. Coimbra, Ling Zhou and Qunming Liu
J. Sol. Energy Eng   doi: 10.1115/1.4036331
In this paper, a Nonlinear Distributed Parameter Dynamic Model (NDPDM) is proposed to model the dynamic behavior of once-through Direct Steam Generator (DSG) collector row under moving shadow conditions. Compared with state-of- the-art models, the proposed NDPDM possesses three unique advantages: (1) adopting real-time local values of a heat transfer coefficient and a friction resistance coefficient, (2) simulating the whole collector row, including the boiler section and the superheated section, and (3) modeling the disturbance of direct normal irradiance (DNI) on DSG collector row under moving shadow conditions. Validated using experimental data, the NDPDM accurately predicts the dynamic characteristics of the Heat Transfer Fluid (HTF) during periods of partial and moving DNI disturbances due to varying cloud cover conditions.
TOPICS: Shades and shadows, Solar energy, Boilers, Modeling, Friction, Heat transfer, Fluids, Superheating, Dynamic models, Heat transfer coefficients
Ravindra D. Jilte, Jayant K. Nayak and Shireesh B. Kedare
J. Sol. Energy Eng   doi: 10.1115/1.4036255
In the present study, an experimental testing facility is created to analyze the heat losses from cylindrical solar cavity. Tests are carried out under temperature range from 225°C to 425°C for a cavity inclination from ? = 0° to 90° in steps of 30°. It is observed that for off-flux investigation of solar cavity receiver, isothermal wall temperature can be established with differential heating arrangement. Total loss is found to be the highest when the cavity aperture is positioned at sideways (? = 0°). It decreases by 43-51% when the cavity is inclined (? = 90°). The conduction loss is found to accounts up to 32-34 % of the total heat loss whereas cavity radiative losses is estimated 13%, 16% and 20% of total heat loss respectively for cavity wall temperature 225°C, 325 °C and 425°C. Convective loss is found to accounts up to 46 - 54 % of total heat loss when the cavity aperture is facing sideways (? = 0°), whereas its value reduces to up to 4 % of total heat loss when the cavity aperture is facing downwards direction (? = 90°). A Nusselt number correlation has been developed for predicting the convective heat loss from open cavity. Nusselt number correlation correlates 80% of data within ±25% deviation, and 100% of data within ±30% deviation.
TOPICS: Cavities, Heat losses, Temperature, Solar energy, Heat conduction, Cavity walls, Test facilities, Wall temperature, Heating

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