Mechanical Engineering / Sustainable Energy Session:

Title:           Modeling of Heat and Mass Transfer in a Negative Pressure Difference Irrigation System
Authors:       S. M. Moniruzzaman, Teruyuki Fukuhara
Abstract:     The limited water resource is a main constraint on agricultural production in arid and semi arid regions. Negative pressure difference irrigation (NPDI) system can be one of the highly efficient water saving methods because it applies water directly to the root zone. The NPDI system is composed of a porous pipe buried vertically or horizontally in soil, a water supply conduit and a water reservoir. The water reservoir is placed lower than the porous pipe to make negative water pressure, Pn in the porous pipe. When the matric potential, ψ, of the surrounding soil is smaller than Pn, water moves from the water reservoir into the porous pipe and seeps into the soil. On the contrary, when ψ is larger than Pn, the seepage stops automatically without any artificial work. This study proposes a numerical model to predict heat and mass transfer in a NPDI system and describes laboratory experimental results from which this model was derived. The experiments were conducted by using a porous pipe, a water reservoir, four heating lamps and a soil column filled with Kawanishi sand. The temporal variations in supplied water, soil water storage, evaporation and soil temperature were calculated by the proposed model. The calculated results were in good agreement with the experimental results. The margin of error of the water balance was in the range of 2 to 5 %. It was concluded that the proposed model is valid for an optimal design of the NPDI system.

Keywords:   Heat transfer, mass transfer, numerical model, heat balance, water balance
Pages:         468-476

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