抄録
As pump irrigation systems serve a major portion of irrigated areas in Bangladesh, knowledge of pump discharge is part of the basic information needed for proper planning, designing, installing and managing these systems. Pump discharge is almost never measured in irrigation and water management area in Bangladesh except at the time of pump installation. Hence this study was undertaken to develop a portable type of orifice meter for shallow tubewells which is relatively easy to transport and handle, is readily computable and can be made out of materials which are available everywhere at a reasonable price.
The theoretical approach to fabricating this orifice meter was similar to the principle for an end-cap orifice meter except that the X-sectional area of the vena contracta replaces the X-sectional area of the throat of the end-cap orifice meter.
The orifice opening was made of glass having thickness less than 1/30 th of the pipe diameter (ASME, 1959), as a rectangle shape which is termed “Slit-Orifice Meter”. This opening can be adjusted as per the requirement for the amount of discharge to be measured.
A number of trials compared the predicted and actual discharge measurement with slit-openings of 1.2, 1.6, and 1.7-inch. On the basis of the degree of dependability of discharge level with respect to a wider range of head variation, sensitivity, personal observation, and fitness of equations between predicted and actual discharge by L.S.D., a slit-opening of 1.6-inch was considered to be the most suitable for measuring the pump discharge of a 4-inch delivery pipe.
