ir is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8 n-long tubes inside which the refrigerant is evaporating at -20°C. Air approaches the tube °C and 1 atm with a mean velocity of 5 m/s. The tubes are arranged staggered with longitu L = ST = 1.5 cm. There are 25 rows in the flow direction with 15 tubes in each row. Assume 5°C and the properties of air at this temperature and 1 atm are (Table A-15) k = 0.02326 W/t 316 kg/m3, Pr = 0.7375, µ = 1.705 × 10¬5 kg/m-s, and Prs = Pr@ Ts = -20°C = 0.7408. Also, th emperature of O°C (for use in the mass flow rate calculation at the inlet) is pi = 1.292 kg/m³.

ir is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8 n-long tubes inside which the refrigerant is evaporating at -20°C. Air approaches the tube °C and 1 atm with a mean velocity of 5 m/s. The tubes are arranged staggered with longitu L = ST = 1.5 cm. There are 25 rows in the flow direction with 15 tubes in each row. Assume 5°C and the properties of air at this temperature and 1 atm are (Table A-15) k = 0.02326 W/t 316 kg/m3, Pr = 0.7375, µ = 1.705 × 10¬5 kg/m-s, and Prs = Pr@ Ts = -20°C = 0.7408. Also, th emperature of O°C (for use in the mass flow rate calculation at the inlet) is pi = 1.292 kg/m³.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter6: Forced Convection Over Exterior Surfaces

Section: Chapter Questions

Problem 6.42P

See similar textbooks

Similar questions

7.43 Liquid sodium is to be heated from 500 K to 600 K by passing it at a flow rate of 5.0 kg/s through a 5-cmID tube whose surface is maintained at 620 K. What length of tube is required?
5.7 The average Reynolds number for air passing in turbulent flow over a 2-m-long, flat plate is . Under these conditions, the average Nusselt number was found to be equal to 4150. Determine the average heat transfer coefficient for an oil having thermal properties similar to those in Appendix 2, Table 18, at at the same Reynolds number and flowing over the same plate.
Determine the convection heat transfer coefficient (in W/m?.K) for air flowing at a velocity of 3 m/s in a 10-cm diameter and 10-m long tube. Air enters the tube at 10°C and leaves at 20°C, i.e. air is heated. Take the property of air at 1 atm and assume flow to be fully developed. For air at 1 atm: Temperature k, W/m-K v, m?/s Pr 15°C 0.02476 1.470x10-5 0.7323 20°C 0.02514 1.516x10-5 0.7309 25°C 0.02551 1.562x105 0.7296 Hint: When the fluid temperature changes, we use its properties at mean temperature, unless otherwise specified. Round your answer to 2 decimal places.
A steam reservoir is covered by a rectangular plate (its length is 1 m and width 2 m). The steam temperature is 95o C, and it is in contact with the plate. Over the outside surface of the plate, water is flowing at a speed of 3 m/sec at a temperature of 25o C. What is the mean Nusselt number over the plate? What is the mean heat transfer convective coefficient over the plate? What is the heat transfer rate to the water?
7-115 Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.8-m-long tubes inside which the refrigerant is evaporating at –20°C. Air approaches the tube bank in the normal direction at 0°C and 1 atm with a mean velocity of 5 m/s. The tubes are arranged in-line with longitudinal and transverse pitches of SL = ST = 1.5 cm. There are 25 rows in the %D flow direction with 15 tubes in each row. Determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. Evaluate the air properties at an assumed mean temperature of -5°C and 1 atm. Is this a good assumption? 0.8 m Air 0°C 1 atm ST = 1.5 cm 5 m/s 0.8 cm 1.5 cm/ S, = Refrigerant, –20°C FIGURE P7–115
Water at 15ºC is to be heated to 65ºC by passing it over a bundle of 4-m-long 1-cm-diameter resistance heater rods maintained at 90ºC. Water approaches the heater rod bundle in normal direction at a mean velocity of 0.8 m/s. The rods arc arranged in-line with longitudinal and transverse pitches of SL 4 cm and ST 3 cm. Determine the number of tube rows NL in the flow direction needed to achieve the indicated temperature rise.
Air at 3*10-4 kg/s and 27°C enters a rectangular duct that is 1 m long and 4 mm x 16 mm on the sides. A uniform heat flux of 600 W/m2 is imposed on the duct surface. What is the mean temperature of the duct and the duct surface at the outlet?
Please help with this questionHot carbon dioxide exhaust gas at 1 atm is being cooled by flat plates. Thegas at 220°C flow is parallel over the upper and lower surfaces of a 3-m-longflat plate at a velocity of 3 m/s. If the flat plate surface temperature ismaintained at 80°C.Determine the local convection heat transfer coefficient at 1 m fromthe leading edge and calculate the average convection heat transfer coefficient over theentire plate.
Air at 27 ⁰C and 1 atm flows over a flat plate at a velocity of 3m/s, assuming the plate is heated its entire length to a temperature of 70⁰C. Heat transferred in first 25 cm of the plate is?
A 4m x 4m flat piale maintained at a constant temperature of NOC is subjected to parallel flow of nit at I am. 20 ', and 10 m's. The total drag force acting on the upper surface of the plate is measured to be 2.4N Determine the average convection hear transfer coefficient, and the rate of heat transfer between the upper surface of the plate and the air. The properties of air at 20 ° C and 1 atm from tables, are
What is the length of tubing required to cool air from 80°C to 20°C via an isothermal tube maintained at 0°C? The tube diameter is 20 cm. Mean velocity of air is 4 m/s. Assume the flow to be fully-developed.
During air cooling of oranges, grapefruit, andtangelos, the heat transfer coefficient for combined convection,radiation, and evaporation for air velocities of0.11 < V < 0.33 m/s is determined experimentally and isexpressed as h = 5.05 kair Re1/3/D, where the diameter Dis the characteristic length. Oranges are cooled by refrigeratedair at 5°C and 1 atm at a velocity of 0.3 m/s. Determine(a) the initial rate of heat transfer from a 7-cm-diameterorange initially at 15°C with a thermal conductivity of0.50 W/m·K, (b) the value of the initial temperature gradientinside the orange at the surface, and (c) the value of theNusselt number.