nnoD :s D betae u 3. Temperature Rise in a Heating Wire. A current of 250 A is passing through stainless-steel wire having a diameter of 5.08 mm. The wire is 2.44 m long and has a resistance of 0.0843 N . The outer surface is held constant at 427.6 K. The thermal conductivity is k 22.5 W/m K. Calculate the center-line temperature at steady state. evard bae 0S 008 i 4R FO Ins

nnoD :s D betae u 3. Temperature Rise in a Heating Wire. A current of 250 A is passing through stainless-steel wire having a diameter of 5.08 mm. The wire is 2.44 m long and has a resistance of 0.0843 N . The outer surface is held constant at 427.6 K. The thermal conductivity is k 22.5 W/m K. Calculate the center-line temperature at steady state. evard bae 0S 008 i 4R FO Ins

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.10P: 1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss...

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2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
A current of 200 A is passed through a stainless steel wire (k = 19 W/m.K) 3 mm in diameter. The resistivity of the steel is 70x10^(-6) ohm.cm, and the length of the wire is 1 m. The wire is submerged in a liquid at 383 K and experiences a convection heat transfer coefficient of 4 kW/m^2. K. The center temperature (in K) of the wire is
A 5 mm copper rod of conductivity 398 W/(mK) and length 20 cm is exposed to air. The air temperature is 20 C and convective coefficient is 100 W/(m^2C). Base temperature is 100 C. Determine the temperature of the rod at a distance of 15 cm from the base?
A 10-cm diameter pipe is covered by 2 layers of lagging. The insidelayer is 4 cm thick and has a coefficient of thermal conductivity of 0.08W/m-K. The outside layer is 3cm thick and has a coefficient of thermalconductivity of 0.15 W/m-K. The steam main conveys steam apressure of 1.7 MPa with 25 C superheat. The outside temperature ofthe lagging is 27 C. If the steam main is 30 m long, determine theinterface temperature of the lagging and overall coefficient of heattransfer based on outside area.
A cast iron pipe is used to transfer steam with an inlet temperature of 350 C. Inner radius of the pipe is 5 cm. The thickness of the pipe (k=20 W/(mK)) is 0.5 cm and there is an insulation (k=0.07 W/mK) over the pipe with a thickness of 4 cm. Environmental temperature is -5 C. Determine the steady heat loss from the pipe if the steam convection coefficient is 70 W/(m^2K) and environment convection coefficient is 20 W/(m^2K)? Is insulation thickness enough? a)167 W, yes b)187 W, yes c)147 W, yes d)120 W, no e)none
In a steel tube (thermal conductivity λ=52.9 W/mK , internal diameter di=(=0.098-0.006} m, external diameter =0.098 m), with an internal surface temperature of ϑi=21.4°C and with the external surface temperature of ϑe=55.3°C, calculate the temperature in the radius r=0.04714 m.
A cast iron pipe is used to transfer steam with an inlet temperature of 300 C. Inner radius of the pipe is 15 cm. The thickness of the pipe (k=25 W/(mK)) is 0.7 cm and there is an insulation (k=0.05 W/mK) over the pipe with a thickness of 5 cm. Environmental temperature is -8 C. Determine the steady heat loss from the pipe if the steam convection coefficient is 80 W/(m^2K) and environment convection coefficient is 25 W/(m^2K)? Is insulation thickness enough? a)197 W, yesb)207 W, yesc)147 W, yesd)150 W, noe)none
A cast iron pipe is used to transfer steam with an inlet temperature of 300 C. Inner radius of the pipe is 15 cm. The thickness of the pipe (k=25 W/(mK)) is 0.7 cm and there is an insulation (k=0.05 W/mK) over the pipe with a thickness of 5 cm. Environmental temperature is -8 C. Determine the steady heat loss from the pipe if the steam convection coefficient is 80 W/(m^2K) and environment convection coefficient is 25 W/(m^2K)? Is insulation thickness enough?
Aluminum balls are heated up to 580 K and then exposed to air at 283 K to cool down with an average heat transfer coefficient of 25 W/m2·K. The balls are 3 cm in diameter. Find the temperature at r = 0.5 cm after 75 seconds of exposure. Is the lumped capacitance an acceptable solution here? [Ans.: 329 K].
A coil-shaped cooling pipe is made of SS-304 material. This pipe is 1 ft long, 0.4 inch outside diameter, and inch inside diameter. This coil cooling pipe is used to cool the water in the bath. The temperature of the inner coil pipe is 40oF while the outer coil in contact with water is 80oF. The thermal conductivity of SS-304 is a function of temperature where k(T) = 7.75 + (7.78 x 10-3).T where k is in Btu/h.ft.oF and T is in oF. Calculate the rate of heat dissipation in watts! (1287.7)
A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The steam pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe that needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam only decreases slightly to 95%. The temperature of the outer surface of the insulation is assumed to be 25 ° C. The conductive of the pipe material and the situation of no pressure drop in the pipe. A. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam that comes out = Answer kJ / kg. c. Determine the change / loss of steam heat along the flow = Answer watt. d. Determine the minimum required insulation thickness = Answer cm.