Pin fins are to be specified for use in an industrial cooling application. The fins will be subjected to a gas in cross flow at
For fins of equal length and therefore equal mass, which fin has the largest heat transfer rate? Assume the gas properties are those of air at
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Fundamentals of Heat and Mass Transfer
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- A mercury-in-glass thermometer at 40C(OD=1cm) is inserted through a duct wall into a 3 m/s airstream at 66C. This can be modelled as a cylinder in cross-flow, as shown in the figure. Estimate the heat transfer coefficient between the air and the thermometer.arrow_forward2. Calculate the free convection heat transfer coefficient for a plate 6 ft high and 8 ft wide at 120 °F that is exposed to nitrogen at 60 °F. (see attached) 3. Constant Flux Application. Air at 1 atm and 300 °C is cooled as it flows at a velocity of 5.0 m/s through a tube with a diameter of 2.54 cm. Calculate the heat transfer coefficient if a constant heat flux condition is maintained at the wall and the wall temperature is 20 °C above the temperature along the entire length of the tube. (See attached)arrow_forwardEthylene glycol flows at 0.02 kg/s through a 4-mm diameter, thin-walled tube. The tube is coiled and submerged in a well-stirred water bath maintained at 35°C. If the fluid enters the tube at 93°C, what heat rate and tube length are required for the fluid to leave at 41°C? Neglect heat transfer enhancement associated with the coiling. Draw temperature profile. Net fluld The Colled tubing Well- stirred water bath WWarrow_forward
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- It is aimed to produce frozen potatoes in a newly established business. The entry temperature of the cleaned potato to the system is -16 °C, and the desired temperature to reach 10 °C. For this purpose, a refrigerant at -25 °C will be used. In the freezing process, potatoes of certain sizes are placed in the ice cream basket, the basket is immersed in the tank containing the refrigerant and kept during freezing. A cooling system is designed around the tank and 1M Joule per hour removes heat from the tank to keep the temperature of the tank constant at -25 °C. It is desirable to produce potatoes of different shapes. These shapes are spheres with a diameter of 20 mm, a cube with dimensions of 16x16x16 mm and a rectangular prism with a diameter of 12x12x25 mm. In such a process,a. What should be used as refrigerant?b. What is the daily production capacity for each product?c. What would you recommend to increase production capacity?arrow_forwardMerrill et al. (1965) in a series of classic experiments studied the flow of blood in capillary tubes of various diameters. The blood had a hematocrit of 39.3 and the temperature was 20°C. They measured the pressure drop as a function of the flow rate for five tube diameters ranging from 288 to 850 μm. When they expressed the measured pressure drops in terms of the wall shear stress, and the volumetric flow rates in terms of the reduced average velocity, all of the data for the various tube sizes formed, within the experimental accuracy, a single line as predicted by the Rabinowitsch equation expressed in terms of reduced average velocity. From their results they provide the following values of the Casson parameters at 20°C: τy = 0.0289 dynes cm−2 and s = 0.229 (dynes s cm−2)1/2. Using these values for τy and s, show that the equation below for reduced average velocity provides an excellent fit to their data summarized in the following table. (Wall shear stress) τw , dynes cm-2…arrow_forwardAir at 25°C flows at 50 × 10-6 kg/s within 100-mm-long channels used to cool a high thermal conductivity metal mold. Assume the flow is hydrodynamically and thermally fully developed. Air, Tmi = 25°C Mold, T=50°C- Case A Case B (a) Determine the rate of heat transferred, in W, to the air for a circular channel (D = (case A). 10 mm) when the mold temperature is 50°C (b) Consider air flowing under the same conditions as in case A, except now the channel is segmented into six smaller triangular sections. The flow area of case A is equal to the total flow area of case B. Determine the rate of heat transferred, in W, to the air for the segmented channel. (c) Determine the pressure drops for cases A and B, both in Pa.arrow_forward
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- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning