Calculate the convective heat transfer rate via the top and the two side walls of a refrigerated box trailer as shown in the figure. The trailer is cruising at a rate of 70 mph (31.3 m/s). The box trailer dimensions are 16 m long, 4.1 m high, and 2.6 m wide. Assume that the surface of the trailer is at uniform temperature of 10°C. The air temperature is 30°C. Because of the presence of the prime-mover in the front, the air flow can be assumed to be turbulent when it encounters the trailer. 187.4 KW 16 m Walls. 4.1 m 2.6 m Prime-mover

Calculate the convective heat transfer rate via the top and the two side walls of a refrigerated box trailer as shown in the figure. The trailer is cruising at a rate of 70 mph (31.3 m/s). The box trailer dimensions are 16 m long, 4.1 m high, and 2.6 m wide. Assume that the surface of the trailer is at uniform temperature of 10°C. The air temperature is 30°C. Because of the presence of the prime-mover in the front, the air flow can be assumed to be turbulent when it encounters the trailer. 187.4 KW 16 m Walls. 4.1 m 2.6 m Prime-mover

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.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.50P

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Calculate the convective heat transfer rate via the top and the two side walls of a refrigerated box trailer as shown in the figure. The trailer is cruising at a rate of 70 mph (31.3 m/s). The box trailer dimensions are 16 m long, 4.1 m high, and 2.6 m wide. Assume that the surface of the trailer is at uniform temperature of 10°C. The air temperature is 30°C. Because of the presence of the prime-mover in the front, the air flow can be assumed to be turbulent when it encounters the trailer. 187.4 kW Walls. Prime-mover 16 m 2.6 m
A vehicle carrying refrigeration box is moving with a speed of 24 m/s on a road withambient temperature of 323 K. The dimensions of box are 3 m(H) × 4 m (W) × 10 m (L).Assume a wall temperature of 283 K and air flow is parallel to the longest side of the box.Neglecting the heat loss from the front side and backside of the box, calculate heat lossfrom four surfaces. For flow over flat surfaces useNu = 0.036(Re)0.8(Pr)1/3The properties of air at bulk mean temperature are : = 1.165 kg/m3, Pr = 0.701, cp = 1005 J/kg – K,  = 16 × 10–6m2/s
A 0.5-m diameter uninsulated pipe transports high-temperature steam. Its surface temperature is 150°C and it is exposed to air at -10°C. The air moves in cross flow over the pipe with a velocity of 5 m/s. To compute for the Nusselt number of the air flow, what is the exact value of the temperature in °C on which the air properties should be based?
Compute the Nu numbers for air at 40°C flowing with 4 m/s speed over the following: 1) A Copper sphere of 5 cm in diameter with 80°C isothermal surface temperature 2) A circular Aluminum pipe of 6 cm in diameter with 80°C isothermal surface temperature 3) A bank of 20x20 5-mm diameter tubes arranged in-line with center-to-center distance of 20 mm. Each tube is assumed to have isothermal temperature of 80°C. Please show detailed calculations.
A long and wide heated plate is maintained at uniform temperature. You have to calculate the flux from the plate if a fluid is flowing over the plate at 1 m/s. The length of the plate in the direction of the flow is 10 m. The fluid is air. Temperature of the plate is 60°C and temperature of average heat 81-3 u 10°C.
Air at a velocity of 4 m/s and temperature of 30°C flows over a 2 m long rod with a diameter of 5 cm that is maintained at a uniform temperature of 90°C. Find the convective heat flux to the rod. -1786:34/m²
A 20degC water flows to 50cmx60cm flat plate with velocity of 6m/s . The flat plate surface temperature is maintained at 40deg C. The air flows parallel to the 50cm side of the plate. If the kinematic viscosity of water is 78x10-8 m2/s, at what length the flow become turbulent? If the average laminar heat transfer coefficient of water is 7740W/m2 degC, what is the overall heat transfer at the laminar section?
Principles of Convection Heat Transfer EXAMPLE 7: Air at 5°C and 70 kPa flows over a flat plate at 6 m/s. A heater strip 2.5 cm long is placed on the plate at a distance of 15 cm from the leading edge. Calculate the heat lost from the strip per unit depth of plate for a heater surface temperature of 65°C.
Air at 20 ◦ C flows inside a pipe 18-mm-ID having a uniform heat flux of 150 W/m 2 on the surface, the average flow velocity at entry being 1.0 m/s. The air pressure is 2 bar. Determine the value of convection coefficient. If the pipe is 2.5 m long, determine the air exit temperature and the wall temperature at the exit. Assume fully developed hydrodynamic boundary layer.
Air at 10°C and 1 atm is flowing parallel at a velocity of 15.5 m/s over the top flat surface of copper plate. The top surface of the copper plate is 0.03m by 0.03m square. The temperature of copper plate is uniform at 65.6°C. For laminar flow, calculate the dimensionless Reymolds number (Nre) and Nussel number (NNu). Table A.3-3a. Physical Properties of Air at 101.325 kPa (1 Atm Abs), SI Units Bx (Bp²/1?) T (kJ/kg · u x T (Pa ·s, k (W/m 103 (1/K • (°C) T (K) (kg/m³) K) -17.8255.41.379 1.0048 1.62 × 6s or kg/m · s) · K) Npr (1/K) m³) 0.022500.7203.92 2.79 x 108 O 273.21.293 1.0048 1.72 × (0-5 0.024230.7153.65 2.04 × 108 10.0 283.21.246 1.0048 1.78 ×/0 0.024920.7133.53 1.72 x 108 37.8 311.01.137 1.0048 1.90%/0-S 0.027000.7053.22 1.12 x 108 Select one: O A. NRe = 27826.58; NNu =98.58 O B. NRe = 23215.74; NNu =152.68 O C. NRe = 27826.58; NNu = 152.68 O D. NRe = 23215.74; NNu =98.58
Air with free stream temperature of 10 C is flowing over a flat plate (1.5m long and Im wide). The air is flowing along 1.5m side of the plate. The plate is maintained at 90 C. Find the velocity of air required to have a rate of heat dissipation as 3.75 kW. Use the correlations: Nu =0.664Res Pro3 for laminar flow Nu, = (0.037R *-871)Pr for turbulent flow Take the properties p = 1.0877 kg/m u=2.029x10 m/s, k=0.028 W/mK, C,-1.007KJ/kg.K and Pr=0.703 %3D
Air at 20 C is flowing over a flat plate ( 6m long and 1.5m wide). The plate is maintained at 140 C. Find the heat loss from the plate if the air is flowing parallel to 6m side with a velocity of 2 m/s. What is the percentage change in heat transfer if the air flow is parallel to 1.5m side. The properties of air are: p=1.06 kg/m v 2.548x10 m/s, k=0.0295 W/mK and Pr-0.7. Nu =0.664Res Pr1 for laminar flow Nu, = (0.037RE-871)Pr for turbulent flow