Chapter 4, Problem 4.18P

Determine the power requirement of a soldering iron in which the tip is maintained at 400C. The tip is a cylinder 3 mm in diameter and 10 mm long. The surrounding air temperature is 20C, and the average convection heat transfer coefficient over the tip is 20W/m2K. The tip is highly polished initially, giving it a very low emittance.

A current of 200 A is passed through a stainless-steel wire [k=19 W/mK] 3 mm in diameter. Theresistance of the steel may be taken as 0.099 ohm, and the length of the wire is 1 m. The wire issubmerged in a liquid at 110◦C and experiences a convection heat-transfer coefficient of 4 kW/m2K.Calculate the center and surface temperatures of the wire

An insulated steam pipe passes through a room in which the air and walls are at 25°C. The outside diameter of pipe is 70 mm, and its surface temperature and emissivity are 200°C and 0.80, respectively. If the free convection coefficient from the surface to the air is 15 W/m2-K, what is the rate of heat loss from the surface per unit length of pipe?

I REALLY NEED THE ANSWER UNTIL 5:20PM PLEASE A vertical cylindrical container is being cooled in ambient air at 25°C with no air circulation.If the initial temperature of the container surface is 100°C, compute the surfaceheat transfer coefficient due to natural convection during the initial cooling period. Thediameter of the container is 1 m, and it is 2m high.  HELP ME IF MY SOLUTION IS CORRECT, I THINK THIS IS NOT COMPLETE YET. KINDLY HELP ME PLEASE

A spherhe of aluminium is staying in an air atmosphere . Develop an equation of the tempeture distribution inside the sphere, with respect to the time. given: Ti- initial temperature of the aluminium ( homogeneous) Ta- air temperature (constant) k -conduction coefficient of aluminium hinf- convective coefficient air

Please show all steps not Ai generated they have been wrong and I need to understand whats goin on. A steel sphere (AISI 1010), 100 mm in diameter, is coated with a dielectric material layer of thickness 2 mm and thermal conductivity 0.04 W/m • K. The coated sphere is initially at a uniform temperature of 500°C and is suddenly quenched in a large oil bath for which To = 100°C and h = 3000 W/m • K. Estimate the time required for the coated sphere temperature to reach 150°C. Hint: Neglect the effect of energy storage in the dielectric material, since its thermal capacitance (pcV) is small compared to that of the steel sphere.

A silicon chip is encapsulated so that, under steady-state conditions, all the power dissipated by it is transferred by convection for a fluid current with h=1000 W/(m2.K) and Tꚙ=25oC. An aluminum plate (k=237 W/(mK)), 2 mm thick, is placed on the chip surface, the contact resistance on the chip/aluminum interface is 0.5x10-4 (m2.K)/W. If the chip area is 100 mm2 and the maximum allowable temperature is 85 oC, what is the maximum allowable power dissipation on the chip?

PLEASE ANSWER WITH UNIT!!!!! A copper sphere having a diameter of 2 cm is initially at a uniform temperature of 312 F. It is then suddenly exposed to an air-forced- convection environment at 20 C of which the convective heat transfer coefficient is 200 W/m2K. Embedded in the sphere is a thermocouple to measure the temperature as a function of time. How long will it take for the thermocouple to indicate 30 C. What is the time constant for this system? (Density of copper is 8890 kg/m3) , (Specific heat for copper is 398 J/kg.K).

heat and mass transfer An uninsulated steam pipe of 100-mm diameter is routed through a building whose walls and air are at 27°C. Pressurized steam maintains a pipe surface temperature of 147°C, and the coefficient associated with natural convection is h =10 W/m2.K. The surface emissivity is ɛ= 0.8. What is the rate of heat loss per unit length from the steam line?