58. A room contains 25 kg of air at 100 kPa and14°C. The room has a 250 W refrigerator and1kW electric resistance heater. During a coldwinter day, it is observed that both therefrigerator and the heater are runningcontinuously, but the air temperature in theroom remains constant. The rate of heat lossfrom the room during that day is

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Answered: pom has a 250 W re c resistance heater.…

Engineering

Mechanical Engineering

pom has a 250 W re c resistance heater. iCe it is observed t

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

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THERMOFLUID A student living in a 3-m X 4-m X 4-m dormitory room turns on her 100-W fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and heat trans windows are tightly closed and disregarding any heat fer let through the walls and the windows, determine the temperature in the room when she comes back 8 h later. Use specific heat values at room temperature, and assume room to be at 100 kPa and 20°C in the morning she leaves.
ce an answer is submit you will be unable to return to this part. A refrigeration system is to cool bread loaves with an average mass of 390 g from 30°C to -10°C at a rate of 1200 loaves per hour with refrigerated air at -30°C. Take the average specific and latent heats of bread to be 2.93 kJ/kg-°C and 109.3 kJ/kg. Determine the size of the compressor of the refrigeration system, in kW, for a COP of 1.2 for the refrigeration system. 4 The size of the compressor of the refrigeration system is kW.
Before the widespread use of mechanical refrigeration, cooling was provided by ice, which was delivered by icemen and stored in an icebox. In a current application, blocks of ice at Tice = 32°F with a total mass of mice = 500 lbm are placed in a large food-storage icebox that is used to keep food at Tfood = 45°F on a day in which the outdoor temperature is Tamb = 78°F. The rate of heat loss through the walls of the ice box is Q = 2900 Btu/hr. a.) Estimate the amount of time the ice it will take this ice to melt. b.) Compare the rate of cooling provided in ton units to the mass of ice in tons. c.) Define and calculate efficiency for this process. d.) Determine the change in exergy of the ice in this process. e.) Calculate the Second-Law efficiency for this process.
thermodyanmics problem
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A refrigerator operating between -5°C and 27°C has the capacity of 80 tons. Determine the number of watermelons that can be cooled from 27°C to 0°C in 10 hours if each watermelon weighs 10 kg.
A refrigeration system is to cool bread loaves with an average mass of 390 g from 30°C to -10°C at a rate of 1200 loaves per hour with refrigerated air at -30°C. Take the average specific and latent heats of bread to be 2.93 kJ/kg-°C and 109.3 kJ/kg. Determine the rate of heat removal from the breads, in kJ/h. (You must provide an answer before moving to the next part.) The rate of removal of heat from the breads is kJ/h.
At winter design conditions, a house is projected to lose heat at a rate of 60,000 Btu/h. The internal heat gain from people, lights, and appliances is estimated to be 6000 Btu/h. If this house is to be heated by electric resistance heaters, deter- mine the required rated power of these heaters in kW to main- tain the house at constant temperature.
A refrigeration system is to cool bread loaves with an average mass of 390 g from 30°C to -10°C at a rate of 1200 loaves per hour with refrigerated air at -30°C. Take the average specific and latent heats of bread to be 2.93 kJ/kg-°C and 109.3 kJ/kg. Determine the required volume flow rate of air, in m³/h, if the temperature rise of air is not to exceed 8°C. (You must provide an answer before moving to the next part.) m³/h. The required volume flow rate of air is
A man is trapped in a 1000 m3 sealed basement that is initially at 30°C and atmospheric pressure. He decides to cool the room by plugging in a refrigerator and keeping the refrigerator door open. The refrigerator uses 2.0 kW of electricity and has a coefficient of performance COP = 2.5. Assuming the basement is well insulated, what is the temperature of the room after 1 hour?