The chief engineer at a university that is constructing a large number of new student dormitories decides to install a counter flow concentric tube heat exchanger on each of the dormitory shower drains. The thin walled copper drains are of diameter Di = 50 mm. Wastewater from the shower enters the heat exchanger at Th,i= 38°C while fresh water enters the dormitory at Tc,i= 10° The wastewater flows down the vertical wall of the drain in a thin, falling fil , providing hh = 10,000 W/m2. K.If the annular gap is d= 10 mm, the heat exchanger length is L= 1 m, and the water flow rate is m˙ =10 kg/min, determine the heat transfer rate and the outlet temperature of the warmed fresh water.If a helical spring is installed in the annular gap so the fresh water is forced to follow a spiral path from the inlet to the fresh water outlet, resulting in hc = 9050 W/m2.K, determine the heat transfer rate and the outlet temperature of the fresh water.Based on the result for part (b), calculate the daily savings if 15,000 students each take a 10-minute shower per day and the cost of water heating is $0.07/kW.
The chief engineer at a university that is constructing a large number of new student dormitories decides to install a counter flow concentric tube heat exchanger on each of the dormitory shower drains. The thin walled copper drains are of diameter Di = 50 mm. Wastewater from the shower enters the heat exchanger at Th,i= 38°C while fresh water enters the dormitory at Tc,i= 10° The wastewater flows down the vertical wall of the drain in a thin, falling fil , providing hh = 10,000 W/m2. K.If the annular gap is d= 10 mm, the heat exchanger length is L= 1 m, and the water flow rate is m˙ =10 kg/min, determine the heat transfer rate and the outlet temperature of the warmed fresh water.If a helical spring is installed in the annular gap so the fresh water is forced to follow a spiral path from the inlet to the fresh water outlet, resulting in hc = 9050 W/m2.K, determine the heat transfer rate and the outlet temperature of the fresh water.Based on the result for part (b), calculate the daily savings if 15,000 students each take a 10-minute shower per day and the cost of water heating is $0.07/kW.
Refrigeration and Air Conditioning Technology (MindTap Course List)
8th Edition
ISBN:9781305578296
Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Chapter33: Hydronic Heat
Section: Chapter Questions
Problem 18RQ: Why must expansion be considered when sizing finned-tube radiation?
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The heat exchanger is a combination of two words ''Heat'' and ''Exchanger''. It is a mechanical device that is used to exchange heat energy between two fluids.
Question
- The chief engineer at a university that is constructing a large number of new student dormitories decides to install a counter flow concentric tube heat exchanger on each of the dormitory shower drains. The thin walled copper drains are of diameter Di = 50 mm. Wastewater from the shower enters the heat exchanger at Th,i= 38°C while fresh water enters the dormitory at Tc,i= 10° The wastewater flows down the vertical wall of the drain in a thin, falling fil , providing hh = 10,000 W/m2. K.If the annular gap is d= 10 mm, the heat exchanger length is L= 1 m, and the water flow rate is m˙ =10 kg/min, determine the heat transfer rate and the outlet temperature of the warmed fresh water.If a helical spring is installed in the annular gap so the fresh water is forced to follow a spiral path from the inlet to the fresh water outlet, resulting in hc = 9050 W/m2.K, determine the heat transfer rate and the outlet temperature of the fresh water.Based on the result for part (b), calculate the daily savings if 15,000 students each take a 10-minute shower per day and the cost of water heating is $0.07/kW.
Transcribed Image Text:Hot waste water
Warm fresh water
D-
Copper tube
Annulus
Falling film
Cold fresh water
Cool waste water
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