Performance evaluation and solar radiation capture of optimally inclined box type solar cooker with parallelepiped cooking vessel design

摘要

An optimally inclined box type solar cooker with single booster mirror is presented along with design and development of a novel parallelepiped shaped cooking vessel design for efficient cooking especially in winter conditions. The main feature of new parallelepiped shaped design is its longer inclined south wall (facing the sun) and a trapezoidal cavity on the vessel lid for greater heat transfer to the food material. The ends of the vessel towards east and west direction are minimized. The cooking performance parameters of proposed inclined cooker coupled with new vessel design were compared with horizontally placed identical cooker of same material and dimensions coupled with conventional cylindrical vessel design during winter month (January) of the year 2010 at Ludhiana climate (30°N 77°E), India. Results showed that the first and the second figures of merit (F_1 and F_2) for inclined cooker were 0.16 and 0.54 as compared to 0.14 and 0.43 for horizontally placed cooker. Time taken to boil the water t_(boil) and standard cooking power P_n was 37% less and 40% more respectively in parallelepiped shaped cooking vessel of inclined cooker as compared to conventional cylindrical vessel of horizontally placed cooker. A mathematical model is developed to compute the total solar radiation availability on the absorber plate of inclined as well as horizontal cooker which establishes the better cooking performance of the inclined cooker due to greater width of sun rays intercepting the absorber plate and much higher solar radiation capture. In order to maximize the reflected component of the solar radiation flux incident on the absorber plate, optimum inclination angles of the booster mirror (ψ for inclined cooker and λ for horizontal cooker) were computed for all months at selected latitudes of 10, 20,30,40 and 50°N and used in the solar radiation capture model.