Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470501979
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Chapter 11, Problem 11.60P
(a)
To determine
Percent fuel savings for prescribed conditions.
(b)
To determine
Effect of UA on air outlet temperature and fuel savings
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Mechanical engineering : Heat transfer
1. Determine the overall heat transfer coefficient and flow rate required while using a heat exchanger , the water is enetered at 20◦C through the tubes of small single pass and the water comes out with a temperature at 40◦C. 25 kg/min of steam condenses at 60◦C on the shel side ,the area of the exchanger is 12 m2. (The latentheat, hfg, is 2358.7 kJ/kg at 60◦C.)
2 . You have unpainted aluminum siding on your house and the engineerhas based a heat loss calculation on U = 5 W/m2K. You discover thatair pollution levels are such that Rf is 0.0005 m2K/W on the siding.Should the engineer redesign the siding?
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Problem 2
An air-to-air heat recovery unit uses across-flow exchanger with
both fluids unmixed and an airflow rate of 0.5 kg/s on both sides.
The hot air enters at 400 °C while the cool air enters at 20 °C.
Calculate the exit temperatures for U = 40 W/m². °C and a total
exchanger area of 15 m². Take the specific heat of air 1006 J/kg.°c.
Counterflow to cool the oil in the lubrication system of a large industrial gas turbine. A double-pipe heat exchanger is used. Coolant flowing through the inner pipe (Cp=4178) J/kg.°C) and oil flowing through the ring channel (Cp=2005.5 J/kg.°C) mass flow rates are 0.2 and 0.4, respectively kg/s. Oil enters the heat exchanger at 60 oC and leaves at 40 oC. Water inlet temperature 30 is oC. The heat transfer coefficient on the ring side is 500 W/m2K. Diameter of thin-walled inner tube is 25 mm, the inner diameter of the outer ring is 45 mm. Pollution resistance in the inner pipe where city mains water is used It is 0.000176 m2K/W. The deposit on the oil side is negligible. a) The heat transfer coefficient in the inner pipe b) Total heat transfer coefficient, c) Calculate the length of the heat exchanger. d) If a 4 m long hairpin is used in the heat exchanger, the required number of hairpins set.
Chapter 11 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 11 - In a fire-tube boiler, hot products of combustion...Ch. 11 - A shell-and-tube heat exchanger is to heat an...Ch. 11 - A steel tube (k=50W/mK) of inner and outer...Ch. 11 - A heat recovery device involves transferring...Ch. 11 - A novel design for a condenser consists of a tube...Ch. 11 - The condenser of a steam power plant...Ch. 11 - Thin-walled aluminum tubes of diameter D = 10mmare...Ch. 11 - A tinned-tube, cross-how heat exchanger is to use...Ch. 11 - Water at a rate of 45,500kg/h is heated from 80...Ch. 11 - A novel heat exchanger concept consists of a...
Ch. 11 - Prob. 11.12PCh. 11 - A process fluid having a specific heat of...Ch. 11 - A shell-and-tube exchanger (two shells, four tube...Ch. 11 - Consider the heat exchanger of Problem 11.14....Ch. 11 - The hot and cold inlet temperatures to a...Ch. 11 - A concentric tube heat exchanger of length L = 2 m...Ch. 11 - A counterflow, concentric tube heat exchanger is...Ch. 11 - Consider a concentric tube heat exchanger with an...Ch. 11 - A shell-and-tube heat exchanger must be designed...Ch. 11 - A concentric tube heat exchanger for cooling...Ch. 11 - A counterflow, concentric tube heat exchanger used...Ch. 11 - An automobile radiator may be viewed as a...Ch. 11 - Hot air for a large-scale drying operation is to...Ch. 11 - In a dairy operation, milk at a flow rate of 250...Ch. 11 - The compartment heater of an automobile...Ch. 11 - A counterflow, twin-tube heat exchanger is made...Ch. 11 - Consider a coupled shell-in-tube heat exchange...Ch. 11 - For health reasons, public spaces require the...Ch. 11 - A shell-and-tube heat exchanger (1 shell pass, 2...Ch. 11 - Saturated water vapor leaves a steam turbine at a...Ch. 11 - The human brain is especially sensitive to...Ch. 11 - Prob. 11.47PCh. 11 - A plate-tin heat exchanger is used to condense a...Ch. 11 - In a supercomputer, signal propagation delays...Ch. 11 - Untapped geothermal sites in the United States...Ch. 11 - A shell-and-tube heat exchanger consists of 135...Ch. 11 - An ocean thermal energy conversion system is...Ch. 11 - Prob. 11.55PCh. 11 - Prob. 11.56PCh. 11 - The chief engineer at a university that is...Ch. 11 - A shell-and-tube heat exchanger with one shell...Ch. 11 - Prob. 11.59PCh. 11 - Prob. 11.60PCh. 11 - Prob. 11.61PCh. 11 - Prob. 11.62PCh. 11 - A recuperator is a heat exchanger that heats air...Ch. 11 - Prob. 11.64PCh. 11 - Prob. 11.65PCh. 11 - A cross-flow heat exchanger consists of a bundle...Ch. 11 - Exhaust gas from a furnace is used to preheat the...Ch. 11 - Prob. 11.68PCh. 11 - A liquefied natural gas (LNG) regasification...Ch. 11 - Prob. 11.70PCh. 11 - A shell-and-tube heat exchanger consisting of...Ch. 11 - Prob. 11.73PCh. 11 - The power needed to overcome wind and friction...Ch. 11 - Prob. 11.75PCh. 11 - Consider a Rankine cycle with saturated steam...Ch. 11 - Consider the Rankine cycle of Problem 11.77,...Ch. 11 - Prob. 11.79PCh. 11 - Prob. 11.80PCh. 11 - Hot exhaust gases are used in a...Ch. 11 - Prob. 11.84PCh. 11 - Prob. 11.90PCh. 11 - Prob. 11S.1PCh. 11 - Prob. 11S.2PCh. 11 - Prob. 11S.3PCh. 11 - Solve Problem 11.15 using the LMTD method.Ch. 11 - Prob. 11S.5PCh. 11 - Prob. 11S.6PCh. 11 - Prob. 11S.8PCh. 11 - Prob. 11S.10PCh. 11 - Prob. 11S.11PCh. 11 - A cooling coil consists of a bank of aluminum...Ch. 11 - Prob. 11S.17P
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- 1. A crossflow heat exchanger, one fluid mixed and one unmixed (oil in tubes and steam in shell), is used to heat an oil in the tubes (c = 1.9 kJ/kg°C) from 15°C to 85°C. Steam (5.2 kg/s, c = 1.86 kJ/kg°C) blows across the outside of the tube, enters at 130°C and leaves at 110°C. U. = 275 W/m²K. Calculate A. [10.84 m²]arrow_forwardAn air-cooled condenser has an h value of 30 W/m2-K based on the air-side area. The air-side heat transfer area is 190 m2 with air entering at 27°C and leaving at 40°C. If the condensing temperature is constant at 49°C, what is the air mass flow rate in kg/s? Let Cp(air) = 1.006 kJ/kg-K. Draw and label the temperature-flow diagram. Round off your answer to three (3) decimal places.arrow_forwardFor two heat exchangers under similar conditions except that one is cross flow and the other one is parallel flow, the amount of heat transfer of the cross flow heat exchanger should be higher than that of the parallel flow heat exchanger, for a given heat transfer area. Select one: O True O False In a condenser, the driving force of the heat transfer process is the fluid velocity. Select one: O True O False Heating a fluid flowing inside a closed circular conduit or pipe is the most important conductive heat-transfer process industry. Select one: O True O Falsearrow_forward
- 2. A heat exchanger like that is used to heat an oil in the tubes (c = 1.9 kJ/kg °C) from 15-C to 85 °C. Blowing across the outside of the tubes is steam that enters at 130-C and leaves at 110°C with a mass flow of 5.2 kg/sec. The overall heat-transfer coefficient is 275 W/m² °C and c for steam is 1.86 kJ/kg C. Calculate the surface area of the heat exchanger (Holman, 2002). 130 85 Steam Oil 110arrow_forwardA cross flow heat exchanger (Both fluids are mixed) Is used to heat oil in the tubes (c=1.8 kj/kg · ◦c) from 15◦c to 85◦c with a mass flow of 0.73kg/sec. blowing across the outside of the tubes is steam that enters at 130◦c and leaves at 110◦c with a mass flow of 5.3 kg/sec. The overall heat-transfer coefficient is 270 w/m2◦c and c for steam is 1.96kj/kg◦c. The surface area of the heat exchanger is 12 m2. Calculate effectiveness of this heat exchanger. (Note: Select suitable formula form formula sheet)arrow_forwardQuestion 2 En. Karim recently install a hot water system operates by a solar energy. The system consists of double pipe counter flow heat exchanger. Cold waters enters a tube at 22°C at a rate of 0.1 kg/s, while hot air enters the heat exchanger at 90°C at a rate of 0.3 kg/s. The specific heat for both cold water and hot air is cp = 4180 J/kg.K and c, = 1010 J/kg.K , respectively. The overall heat transfer coefficient based on the inner side of the tube is 80 W/m².K. The length of the tube is 12 m and the internal diameter of the tube is 1.2 cm. En. Karim assigned you do the complete analysis on this hot water system including to calculate the effectiveness of the heat exchanger. As an engineer, you have to determine: i. the heat capacity rates of both fluids, ii. the maximum rate of heat transfer (kW), iii. the effectiveness of the heat exchanger (NTU method), iv. the actual rate of heat transfer (kW), and v. the outlet temperatures of both cold water and hot air.arrow_forward
- A single-pass, cross-flow heat exchanger uses hot exhaust gases (mixed) to heat water (unmixed) from 30°C to 80°C at a rate of 5.25 kg/s. The exhaust gases enter and exit the exchanger at 225°C and 100°C, respectively. What is the mass flow rate of the hot gases (kg/s) ? Water : c = 4184 J/kg K, Hot gases 1019 J/kg K p Select one:arrow_forwardHERE ARE SOME APPLICATIONS OF SHEEL AND TUBE HEAT EXCHANGER: Power Generation HVAC Marine Applications Pulp and Paper Refrigeration Pharmaceuticals Air Processing and Compressor Cooling Metals and MiningPLEASE MAKE A EXPLANATION FOR THISarrow_forwardA heat exchanger is heating water from 50 0 F to 160 0 F using steam on the shell at atmospheric pressure condensing at 212 0 F. If the overall U is 710 BTU/(hr 0 F ft2) and the exchange rate is 9,000,000 BTU/hr, what tube area is needed?arrow_forward
- 2- In a heat exchanger, steam of 0.08 bar and a specific steam content of 95% is condensed. 381.6 tons / h cooling water with a temperature of 10 ̊C flows in parallel connected tubers with inner / outer diameter 28/30 mm with a speed of 0.65 m / s. The heat transfer surface of the heat exchanger is 220 m2 and it has a k-value of 2200 W / (m2K) . Assume the specific heat capacity of the water 4.18 kJ / (kg K) and density 1000 kg / m3. The K-value is attributed to the outer mantle surface of the tubes. a) Calculate the outlet temperature of cooling water. b) How many tonnes of steam per hour are condensed? c) Determine the number of tubes and tube lengtharrow_forwardA counterflow, concentric tube heat exchanger is used to cool the lubricating oil for a large industrial gas turbine engine. The flow rate of cooling water through the inner tube (D; = 25 mm) is 0.2 kg/s, while the flow rate of oil through the outer annulus (D = 45 mm) is 0.1 kg/s. The oil and water enter at temperatures of 100 and 30°C, respectively. How long must the tube be made if the outlet temperature of the oil is to be 60°C?arrow_forwardQUESTION 7 A local brand of water heater has offered a counterflow concentric tube heat exchanger, consisting of thin walled copper drains with a diameter D; = 50 mm. Waste water from the shower enters the heat exchanger at Thi= 38 °C while fresh water enters the room at Te,j= 10 °C. The waste water flows down the vertical drain wall in a thin, falling film and providing h, = 10 kW/m²·K. i. 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 outlet temperature of the warmed fresh water. ii. If a helical spring is installed in an annular gap so the fresh water is forced to flow a spiral path from the inlet to the fresh water outlet, resulting in he = 9050 W/m²-K, determine the heat transfer rate and outlet temperature of the fresh water. iii. Based on the result from Q5(b), calculate the daily saving if 15,000 guests each take 10 minutes shower per day and cost of water heating is…arrow_forward
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