Bissoy.com
Doctors Medicines MCQs Q&A

A small light bulb (25 W) inside a refrigerator is kept on and 50 W of energy from the outside seeps into the refrigerated space. How much of temperature difference to the ambient(at 20°C) must the refrigerator have in its heat exchanger having an area of 1 m2 and heat transfer coefficient of 15 W/Km2 to reject the leak of energy.

A small light bulb (25 W) inside a refrigerator is kept on and 50 W of energy from the outside seeps into the refrigerated space. How much of temperature difference to the ambient(at 20°C) must the refrigerator have in its heat exchanger having an area of 1 m2 and heat transfer coefficient of 15 W/Km2 to reject the leak of energy. Correct Answer 5°C

Total energy that goes out = 50+25 = 75 W 75 = hA∆T = 15 × 1 × ∆T hence ∆T = 5°C.

Related Questions

In this question, a passage and a related statement have been given. Read the passage carefully and assess the statement based on it. Using knives and screws, two Russian astronauts on Tuesday took a sample of substance around a mysterious cavity of the spacecraft called the Soyuz, which was placed in the International Space Station, a Moscow official suggested that it was a break - It can also be done. In August, two months after the last visit of the vehicle, the air leak was detected in the Soyuz spacecraft due to the 2 mm air in the ISS. Roskosmos, an astronomical institute, says that cutting off the insulation on the hole and sampling the material around it and the purpose of putting a new insulation on it is to find out that this small but dangerous hole has been done on earth or Is in space. The chief of Roskosmos has said that the error of manufacturing has not been found in the investigation. Experienced astronauts had to struggle but they managed their mission. Before the spacewalk, astronauts were able to inspect the hole just from within the spacecraft. The biggest difficulty was that in the Soyuz spacecraft, the ISS was not designed to improve during adverse weather space, and no railing was also made to catch the space passengers outside the vehicle. Statement: In the Soyuz spacecraft, the air leak due to the presence of the leak was detected after two months of the last visit. Select the appropriate from the given options A - Statement is completely true B - The statement is possibly true C - the statement can not be determined D - Statement is completely false
Consider the following statements: 1. The operation of a refrigerator unit at more than one temperature can be accomplished by using different throttling valves and a separate compressor for each ‘temperature range’. 2. The refrigerated space must be maintained above the ice point to prevent freezing. 3. In domestic refrigerators, the refrigerant is throttled to a higher pressure in the freezer followed by full expansion in the refrigerated space. Which of the above statements are correct? 
Two refrigerators M and N operate in series. The refrigerator M absorbs energy at the rate of 1 kW from a body at temperature 400 K and rejects energy as heat to a body at a temperature T. The refrigerator N absorbs the same quantity of energy which is rejected by the refrigerator N from the body at temperature T, and rejects energy as heat to a body at temperature 800 K. If both the refrigerators have the same C.O.P., what is the value temperature T?
In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K
A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as
A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as
Forced air flows over a convection heat exchanger in a room heater, resulting in a convective heat transfer coefficient 1.136 k W/m2 K. The surface temperature of heat exchanger may be considered constant at 65 degree Celsius, and the air is at 20 degree Celsius. Determine the heat exchanger surface area required for 8.8 k W of heating
Which of the following statements about Printed circuit heat exchanger are correct? Statement 1: Printed circuit heat exchanger is an example for direct heat exchanger. Statement 2: It has high heat transfer surface area per unit volume of the exchanger.
In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m2 hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger
In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has a saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to the water. Take specific heat of water as 4 k J/kg K