Small potato balls of 0.5 cm radius (can be approximated as a sphere) baked in the oven and initially at a uniform temperature of 160°C. Assume, potatoes have a density of 650 kg/m³, specific heat of 3400 J/kgK and conductivity of 1 W/mK. You want to eat potatoes quickly without burning your tongue so that you have decided to cool them down with forced convection. Air h, T. hot potato initially @ T Air temperature is 20°c and the convective heat transfer coefficient is 140 W/m²K. Calculate the time (in seconds) required for its surface temperature to drop 90°C. Round the value you calculated and write it as an integer!!! For example, if you find 8.2, write is as 8..

Small potato balls of 0.5 cm radius (can be approximated as a sphere) baked in the oven and initially at a uniform temperature of 160°C. Assume, potatoes have a density of 650 kg/m³, specific heat of 3400 J/kgK and conductivity of 1 W/mK. You want to eat potatoes quickly without burning your tongue so that you have decided to cool them down with forced convection. Air h, T. hot potato initially @ T Air temperature is 20°c and the convective heat transfer coefficient is 140 W/m²K. Calculate the time (in seconds) required for its surface temperature to drop 90°C. Round the value you calculated and write it as an integer!!! For example, if you find 8.2, write is as 8..

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

H.W1 Consider a person standing in a room. Determine the total rate of heat transfer from this person if the exposed surface area and temperature are 1.6m² and 29°C, respectively. Assume that the convection heat transfer coefficient is 6W/m².K and the emissivity of a person is 0.95. The air temperature in the room is maintained at 22°C at all times of the year. In summer, the wall and ceiling temperatures are observed to be 25°C, while in winter, they are 10°C. Ans: Qrotal =104.4 W In Summer Qrotal =231.3 W In Winter
3.4 Estimate the rate of heat loss due to radiation from a covered pot of water at 95 ° C. How does this compare with the 60 W that is lost due only to convection and conduction losses? What amount of energy input would be needed to maintain the water at its boiling point for 30 minutes? The polished stainless steel pot is cylindrical, 20 cm in diameter and 14 cm high, with a tight-fitting flat cover. The air temperature in the kitchen is about 25 ° C. State any assumptions you make in deriving your estimates
3 Brass cube "p = 8530 kg/m , c= side length =9 mm, are annealed by heating them first to 813°C in a furnace and then allowing them to cool slowly to 130°C in ambient air at 28°C. If the average heat transfer coefficient is 19.9 W/m .°C, If 2204 balls are to be annealed per hour, what is the total rate of heat transfer (watts) from the balls to the ambient air? 380 J/kg.°C, k = 110 W/m.°C, a = 33.9E-6 W/m.°C",
You are designing a new eco-friendly thermal coffee mug. It is shaped like a small globe to minimize surface area, which is only about 0.04m^2. You use two 0.003m layers of recyclable PETE which has a thermal conductivity, k, of 0.2W/mK around a 0.01m layer of dead air, with a thermal conductivity of 0.026W/mK. Since this is for hot coffee, use a temperature difference of 40K. Q = Ax (T2-T1) / (R1 + R2 + etc) R =x/k. What is the heat lose through the surface in watts?
= A long rod of 60-mm diameter and thermophysical properties p 8000 kg/m³, c C = 500 J/kg-K, and k = 50 W/m-K is initially at a uniform temperature and is heated in a forced convection furnace maintained at 750 K. The convection coefficient is estimated to be 1000 W/m².K. What is the centerline temperature of the rod when the surface temperature is 570 K? The centerline temperature of the rod is i K.
Small potato balls of 0.5 cm radius (can be approximated as a sphere) baked in the oven and initially at a uniform temperature of 160°C. Assume, potatoes have a density of 650 kg/m, specific heat of 3400 J/kgK and conductivity of 1 W/mK. You want to eat potatoes quickly without burning your tongue so that you have decided to cool them down with forced convection. Air h, T. hot potato initially Air temperature is 20°C and the convective heat transfer coefficient is 140 W/m?K. Calculate the time (in seconds) required for its surface temperature to drop 90°C.
PROCESS INSTRUMENTATION AND CONTROL 4. A 3m X 2m window has an exterior surface temperature of 220C, and the outside wind is blowing air at -60C across it with a convection heat transfer of h= 125W/m2K. What is the total heat transfer loss?
Problem 1: The uniform drum shown weighs 80lb and has a radius of 0.5ft. Starting from rest, the cable wrapped around the drum is subjected to a vertical force P which resulted in a constant angular acceleration of 20 rad/s. Determine magnitude of P and the reaction at the support pin at O. Neglect the mass of the cable d = 20 80 - 2.48 32.2 r-0.5 %3D
2-D: A fin may be manufactured as an integral part of a surface by using a casting or extrusion process, or it may be separately brazed or adhered to the surface. From thermal considerations, which option is preferred? 2-E: What is the difference between steady-state and transient heat transfer processes? Give an example for each of them. 2-F: What is the physical interpretation of the Biot number? 2-G: For flow over a flat plate, sketch variation of local convective heat transfer coefficient, h(x), versus the distance along the plate x for laminar, transition, and turbulent flow regimes.
When operating at steady-state in a 250C room, the surface temperature of a 20 W incandescent light bulb is 1250C. Approximate the bulb as a 40 mm diameter sphere to estimate the rate of heat transfer from the bulb via convection. Air properties: k-0.030 W/m-K Spear surface area: S=4tr²³ v-20.92x10" m²/s Sphere volume: V=(4/3)Tr Pr-0.700
A 50-mm thick plate of carbon steel (AISI 1010) is annealed with a reheat stage taking the steel from its initial uniform temperature of 200 C to a minimum final temperature of 550 C. HEating is effected in a gas-fired furnace where products of combustion at Tamb = 800 C maintain a convection coefficient of h = 100 W/m^2K on both sides of the plate. How long should the plate be left in the furnace? Substantiate with relevant analysis and calculations.