Facilitating cool-hot air mixing inside the heater unit is one of important factors when considering the design of air conditioning systems. In order to produce efficient mixing in the limited space inside the heater unit, conventional guides are provided to control mixing. Because of the difficulties of detailed analysis of air flow inside the heater unit, the shapes and installation positions of these guides were determined empirically. The development of experimental flow analysis utilizing the latest image processing technology and computer-aided numerical analysis contribute remarkably to the design of air conditioning system based upon qualitative and quantitative analysis of actual flow phenomena. In this report, laser-assisted flow visualization and the velocity distribution measuring technique using the speckle method are applied to an experimental analysis of guide effects to cool-hot air mixing in a heater unit model. Additionally, the results of 3-dimensional numerical analysis of the heater unit air flow using standard software are compared with the experimental ones to verify the validity of the method as an effective tool for the heater unit air flow analysis.
Experiments in the four intersecting ducts with intersecting angles of 30°and 60° are performed to investigate the vortex formation in the intersecting region and the flow rates at the end of each duct. The flow characteristics in six types of the four intersecting ducts are clarified by using different lengths of intersecting zones. The fluid control in the four intersecting ducts with the intersecting angle of 30° is found to have particular characteris-tics in fluid engineering. Furthermore, the relationship between the Reynolds number and the Strouhal number in the swing of water jet at the end of the multiple intersecting ducts is disclosed by measuring the frequency of the swing and the flow rates at the end of ducts.
The infrared thermography near ambient conditions is proposed to estimate convective heat transfer quantitatively. The correlation between a radiation temperature and a true temperature is calibrated at first. The surface temperature distribution is then measured for laminar natural convection along a vertical flat plate as one of applications. We further estimate natural cooling fin using the present infrared thermography to confirm the applicability. The measurement error is also estimated using ANSI/ASME PTC 19.1-1985 measurement uncertainty to confirm the accuracy. It is revealed from a series of application experiments and error analyses that the proposed technique of measuring temperature is useful to estimate convective heat transfer quantitatively.