Design and Use of an Apparatus to Teach Theory of Ventilation Inlets for Agricultural Structures

Abstract. An apparatus was designed and built to provide a way for students to learn ventilation inlet theory in a practical laboratory setting. The apparatus was designed to provide an adjustable slot inlet, several fans to vary the air velocity through the inlet from 1.3 to 4.8 m/s, a manometer to measure the static pressure drop across the inlet, ports to allow students to measure inlet velocity, and the variation of velocity with respect to distance from the inlet. The interior of the apparatus was painted black and a large window was installed to allow students to observe the air mixing and distribution achieved by the inlet by way of smoke visualization. The apparatus also allowed students to collect velocity versus static pressure drop data across a variety of inlet sizes. Regression analysis provided students the means to empirically determine the discharge coefficient for an inlet of known opening thickness. The discharge coefficients determined by the students agreed with the literature for slot aspect ratios (w/L) of 0.0080 to 0.0131. It was found that the discharge coefficient was positively correlated with respect to aspect ratio and data were provided for aspect ratios as high as 0.0298. The apparatus has been used to provide laboratory instruction on inlet theory for two semesters in a course on environmental control of agricultural structures. Many students have demonstrated a greater understanding of mechanical ventilation following the laboratory activity.