Thermal losses evaluation of an external rectangular receiver in a windy environment. (15th May 2019)

• Record Type: Journal Article
• Authors: Qaisrani, Mumtaz A.; Fang, Jiabin; Jin, Yabin; Wan, Zhenjie; Tu, Nan; Khalid, Muhammad; Rahman, Mujib Ur; Wei, Jinjia
• Is Part Of: Solar energy. Volume 184(2019)
• Page Start: 281
• Page End: 291
• Publication Date: 2019-05-15
• Subjects: External rectangular receiver -- Wind-blocking walls -- Thermal losses reduction -- Thermal performance; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2019.03.103
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Thermal performance of an external receiver is numerically evaluated. Different wind directions and wind velocities are experimented to evaluate the losses. A novel design using wind blocking walls is tested to successfully reduce the losses. Receiver and wind characteristics dependent correlation is derived to evaluate losses. Abstract: The efficiency of a CSP plant heavily depends on the performance of the receiver. The receiver is responsible for light-heat conversion in a power generation system. With the objective of numerical evaluation of the thermal losses of an external receiver, a method was developed in the present study. Solar flux was obtained on a north-facing receiver using the "SolarPilot" software, through Monte-Carlo ray tracing technique. Apposite boiling heat transfer coefficients were selected and then applied to obtain the temperature at the surface of the boiling tubes. Numerical simulations were performed to quantify the heat losses in the receiver at different wind velocities. Maximum heat flux and temperature were obtained at the center of the receiver. The results indicated that wind direction and wind velocity have a significant impact on the extent of heat losses. Maximum heat losses occur in the side-on wind direction (i.e., west bound) while losses are minimum in the head-on wind direction (i.e., north bound). Thermal losses through the receiver contribute a sizeable portion to overall energy losses in power tower systems, hence, to attenuate the heat losses a new, yet simple, design is proposed with the addition of wind-blocking walls at the receiver's periphery. The walls achieve noticeable heat retention in all wind directions, but their role is more prominent in the head-on wind direction. In best case scenario, attaching 1 m wide wind blocking walls resulted in a diminution of about 33 percent of losses in the head-on wind direction at 9 m/s wind velocity. Results obtained are then employed to derive a simplified correlation model to evaluate convective heat losses as a function of wind direction, wind velocity, receiver's surface area and wind blocking wall width.