Consider laminar flow of a fluid with 3u 4 that undergoes a combined entrance process within a constant surface temperature tube of length / [fdw with a flow rate of . an engineer suggests that the total heat transfer rate can be improved if the tube is divided into 1 shorter tubes, each of length /1 //1 with a flow rate of . determine an expression for the ratio of the heat transfer coefficient averaged over the 1 tubes, each experiencing a combined entrance process, to the heat transfer coefficient averaged over the single tube, .

Calculate the bore of a cylinder that has a stroke of 18 inches and an extension time of 6 seconds at a flow rate of 4 gal/min.

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.

Afan that can provide air speeds up to 60 m/s is to be used in a low-speed wind tunnel with atmospheric air at 35 c. if one wishes to use the wind tunnel to study flat-plate boundary layer behavior up to reynolds numbes of re 10, what is the minimum plate length that should be used? at what distance from the leading edge would transition occur if the critical reynolds nurnber were rer, e = 5 × 105?