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When the outlet temperatures of the fluids in a heat exchanger are not known, is it still practical to use the LMTD method? Explain. For specified inlet and outlet temperatures, for what kind of heat exchanger will the T lm be greatest: double-pipe parallel-flow, double-pipe counter-flow, cross-flow, or multipass shell-and-tube... The density of liquid water can be correlated as Ï(T) = 1000-0.0736T-0.00355T 2 where Ï and T are in kg/m and °C, respectively. Determine the volume expansion coefficient at 70°C.... A stream of hydrocarbon (c p = 2.2 kJ/kgK) is cooled at a rate of 720 kg/h from 150C to 40C in the tube side of a double-pipe counter-flow heat exchanger. Water (c p = 4.18 kJ/ kgK) enters the heat... Glycerin (c p = 2400 J/kgK) at 20C and 0.5 kg/s is to be heated by ethylene glycol (c p = 2500 J/kgK) at 60C in a thin-walled double-pipe parallel-flow heat exchanger. The temperature difference... A heat exchanger contains 400 tubes with inner diameter of 23 mm and outer diameter of 25 mm. The length of each tube is 3.7 m. The corrected log mean temperature difference is 23C, while the inner... A thin-walled double-pipe counter-flow heat exchanger is to be used to cool oil (c p = 2200 J/kgK) from 150C to 40C at a rate of 2 kg/s by water (c p = 4180 J/kgK) that enters at 22C at a rate of 1.5... Cold water (c p = 4180 J/kgK) leading to a shower enters a thin-walled double-pipe counter-flow heat exchanger at 15C at a rate of 1.25 kg/s and is heated to 45C by hot water (c p = 4190 J/kgK) that... Hot exhaust gases of a stationary diesel engine are to be used to generate steam in an evaporator. Exhaust gases (c p = 1051 J/kgK) enter the heat exchanger at 550C at a rate of 0.25 kg/s while water... A vertical 4-ft-high and 6-ft-wide double-pane window consists of two sheets of glass separated by a 1-in air gap at atmospheric pressure. If the glass surface temperatures across the air gap are... In a plant that manufactures canned aerosol paints, the cans are temperature-tested in water baths at 55°C before they are shipped to ensure that they withstand temperatures up to 55°C during... A 2-m-internal-diameter double-walled spherical tank is used to store iced water at 0°C. Each wall is 0.5 cm thick, and the 1.5-cm-thick air space between the two walls of the tank is evacuated... A shell-and-tube heat exchanger with 2-shell passes and 12-tube passes is used to heat water (c p = 4180 J/kgK) in the tubes from 20C to 70C at a rate of 4.5 kg/s. Heat is supplied by hot oil (c p =... Repeat Prob. 2264 for a mass flow rate of 3 kg/s for water. Repeat Prob. A shell-and-tube heat exchanger with 2-shell passes and 12-tube passes is used to heat water (c p = 4180 J/kgK) in the tubes... What does the effectiveness of a heat exchanger represent? Can effectiveness be greater than one? On what factors does the effectiveness of a heat exchanger depend? Consider the two parallel coaxial disks of diameters a and b, shown in Fig. P21132. For this geometry, the view factor from the smaller disk to the larger disk can be calculated from where, A = a/2L,... A large number of long tubes, each of diameter D, are placed parallel to each other and at a center-to-center distance of s. Since all of the tubes are geometrically similar and at the same... Solar radiation is incident on the front surface of a thin plate with direct and diffuse components of 300 and 250 W/m 2 , respectively. The direct radiation makes a 30° angle with the normal of... For a specified fluid pair, inlet temperatures, and mass flow rates, what kind of heat exchanger will have the highest effectiveness: double-pipe parallel-flow, double-pipe counterflow, cross-flow,... Explain how you can evaluate the outlet temperatures of the cold and hot fluids in a heat exchanger after its effectiveness is determined. Can the temperature of the cold fluid rise above the inlet temperature of the hot fluid at any location in a heat exchanger? Explain. Consider a heat exchanger in which both fluids have the same specific heats but different mass flow rates. Which fluid will experience a larger temperature change: the one with the lower or higher... Explain how the maximum possible heat transfer rate Q max in a heat exchanger can be determined when the mass flow rates, specific heats, and the inlet temperatures of the two fluids are specified.... Under what conditions can a counter-flow heat exchanger have an effectiveness of one? What would your answer be for a parallel-flow heat exchanger? Consider a double-pipe counter-flow heat exchanger. In order to enhance heat transfer, the length of the heat exchanger is now doubled. Do you think its effectiveness will also double? Consider a shell-and-tube water-to-water heat exchanger with identical mass flow rates for both the hot- and cold-water streams. Now the mass flow rate of the cold water is reduced by half. Will the... Consider two double-pipe counter-flow heat exchangers that are identical except that one is twice as long as the other one. Which heat exchanger is more likely to have a higher effectiveness? How is the NTU of a heat exchanger defined? What does it represent? Is a heat exchanger with a very large NTU (say, 10) necessarily a good one to buy? Reconsider Prob. 2240. Using an appropriate software, investigate the effects of temperature and mass flow rate of geothermal water on the length of the tube. Let the temperature vary from 100C to... The radiator in an automobile is a cross-flow heat exchanger (UA s = 10 kW/K) that uses air (c p = 1.00 kJ/kgK) to cool the engine-coolant fluid (c p = 4.00 kJ/kgK). The engine fan draws 30C air... Consider an oil-to-oil double-pipe heat exchanger whose flow arrangement is not known. The temperature measurements indicate that the cold oil enters at 20C and leaves at 55C, while the hot oil... Consider the flow of engine oil (c p = 2048 J/kg·K) through a thin-walled copper tube at a rate of 0.3 kg/s. The engine oil that enters the copper tube at an inlet temperature of 80°C is... In a parallel flow heat exchanger, hot fluid enters the heat exchanger at a temperature of 150C and a mass flow rate of 3 kg/s. The cooling medium enters the heat exchanger at a temperature of 30C... A counter-flow heat exchanger is stated to have an overall heat transfer coefficient of 284 W/m 2 ·K when operating at design and clean conditions. Hot fluid enters the tube side at 93°C... Reconsider Prob. 2249. Using an appropriate software, investigate the effects of oil exit temperature and water inlet temperature on the overall heat transfer coefficient of the heat exchanger. Let... Steam is to be condensed on the shell side of a 1-shell-pass and 8-tube-passes condenser, with 50 tubes in each pass at 90°F (h fg = 1043 Btu/lbm). Cooling water (c p = 1.0 Btu/lbm·°F)... Water (c p = 4180 J/kgK) is to be heated by solarheated hot air (c p = 1010 J/kgK) in a double-pipe counter-flow heat exchanger. Air enters the heat exchanger at 90C at a rate of 0.3 kg/s, while... A thin-walled double-pipe, counter-flow heat exchanger is to be used to cool oil (c p = 0.525 Btu/lbmF) from 300F to 105F at a rate of 5 lbm/s by water (c p = 1.0 Btu/lbmF) that enters at 70F at a... A one-shell and two-tube type heat exchanger has an overall heat transfer coefficient of 300 Btu/hft 2 F. The shell side fluid has a heat capacity rate of 20,000 Btu/hF, while the tube side fluid has... Reconsider Prob. 2252E. Using an appropriate software, investigate the effect of the condensing steam temperature on the rate of heat transfer, the rate of condensation of steam, and the mass flow... Reconsider Prob. 2254. Using an appropriate software, investigate the effect of the exhaust gas inlet temperature on the rate of heat transfer, the exit temperature of exhaust gases, and the rate of... In a textile manufacturing plant, the waste dyeing water (c p = 4295 J/kg·K) at 75°C is to be used to preheat fresh water (c p = 4180 J/kg·K) at 15°C at the same flow rate in a... A performance test is being conducted on a doublepipe counter-flow heat exchanger that carries engine oil and water at a flow rate of 2.5 kg/s and 1.75 kg/s, respectively. Since the heat exchanger... In a one-shell and two-tube heat exchanger, cold water with inlet temperature of 20C is heated by hot water supplied at the inlet at 80C. The cold and hot water flow rates are 5000 kg/h and 10,000... A double-pipe parallel-flow heat exchanger is to heat water (c p = 4180 J/kgK) from 25C to 60C at a rate of 0.2 kg/s. The heating is to be accomplished by geothermal water (c p = 4310 J/kgK)... A shell-and-tube heat exchanger with 2-shell passes and 12-tube passes is used to heat water (c p = 4180 J/kgK) with ethylene glycol (c p = 2680 J/kgK). Water enters the tubes at 22C at a rate of 0.8... A shell-and-tube heat exchanger with 2-shell passes and 8-tube passes is used to heat ethyl alcohol (c p = 2670 J/kgK) in the tubes from 25C to 70C at a rate of 2.1 kg/s. The heating is to be done by... In an industrial facility a counter-flow double-pipe heat exchanger uses superheated steam at a temperature of 250°C to heat feed water at 30°C. The superheated steam experiences a... Reconsider Prob. 2262. Using an appropriate software, investigate the effect of the mass flow rate of water on the rate of heat transfer and the tubeside surface area. Let the mass flow rate vary... A single-pass cross-flow heat exchanger is used to cool jacket water (c p = 1.0 Btu/lbm·°F) of a diesel engine from 190°F to 140°F, using air (c p = 0.245 Btu/lbm·°F)... In a one-shell and eight-tube pass heat exchanger, the temperature of water flowing at rate of 50,000 lbm/h is raised from 70F to 150F. Hot air (c p = 0.25 Btu/lbmF) that flows on the tube side... Air (c p = 1005 J/kgK) enters a cross-flow heat exchanger at 20C at a rate of 3 kg/s, where it is heated by a hot water stream (c p = 4190 J/kgK) that enters the heat exchanger at 70C at a rate of 1... Reconsider Prob. 2285. Using an appropriate software, investigate the effects of the mass flow rate of water and the tube length on the outlet temperatures of water and air. Let the mass flow rate... Cold water (c p = 4180 J/kg·K) leading to a shower enters a thin-walled double-pipe counter-flow heat exchanger at 15°C at a rate of 0.25 kg/s and is heated to 45°C by hot water (c p =... Ethylene glycol is heated from 25C to 40C at a rate of 2.5 kg/s in a horizontal copper tube (k = 386 W/mK) with an inner diameter of 2.0 cm and an outer diameter of 2.5 cm. A saturated vapor (T g =... Oil is being cooled from 180°F to 120°F in a 1-shell and 2-tube heat exchanger with an overall heat transfer coefficient of 40 Btu/h·ft 2 ·°F. Water (c pc = 1.0... Consider a water-to-water double-pipe heat exchanger whose flow arrangement is not known. The temperature measurements indicate that the cold water enters at 20C and leaves at 50C, while the hot... Oil in an engine is being cooled by air in a crossflow heat exchanger, where both fluids are unmixed. Oil (c ph = 2047 J/kg·K) flowing with a flow rate of 0.026 kg/s enters the heat exchanger... Consider a recuperative cross-flow heat exchanger (both fluids unmixed) used in a gas turbine system that carries the exhaust gases at a flow rate of 7.5 kg/s and a temperature of 500°C. The air... Consider operation of a single pass cross-flow heat exchanger with water (c p = 4193 J/kgK) (mixed) and methanol (c p = 2577 J/kgK) (unmixed). Water entering and exiting the heat exchanger at 90C and... Consider a cross-flow engine oil heater that uses ethylene glycol flowing at a temperature of 110°C to heat the oil initially at 10°C. The ethylene glycol enters a tube bank consisting of... By taking the limit as T 2 T 1 , show that when T 1 = T 2 for a heat exchanger, the T lm relation reduces to T lm = T 1 = T 2 . A shell-and-tube heat exchanger with two-shell passes and 4-tube passes is used for cooling oil (c p = 2.0 kJ/kgK) from 125C to 55C. The coolant is water, which enters the shell side at 25C and... Saturated water vapor at 100°C condenses in a 1-shell and 2-tube heat exchanger with a surface area of 0.5 m 2 and an overall heat transfer coefficient of 2000 W/m 2 ·K. Cold water (c pc =... Reconsider Prob. 22107. Using an appropriate software, investigate the effects of the condensing steam temperature and the tube diameter on the rate of heat transfer and the rate of condensation of... Consider a closed loop heat exchanger that carries exit water (c p = 1 Btu/lbmF and = 62.4 lbm/ft 3 ) of a condenser side initially at 100F. The water flows through a 500 ft long stainless steel... Consider the flow of saturated steam at 270.1 kPa that flows through the shell side of a shell-and-tube heat exchanger while the water flows through 4 tubes of diameter 1.25 cm at a rate of 0.25 kg/s... A shell-and-tube heat exchanger with 1-shell pass and 14-tube passes is used to heat water in the tubes with geothermal steam condensing at 120°C (h fg = 2203 kJ/kg) on the shell side. The tubes... A shell-and-tube heat exchanger is used for cooling 47 kg/s of a process stream flowing through the tubes from 160C to 100C. This heat exchanger has a total of 100 identical tubes, each with an... A two-shell passes and four-tube passes heat exchanger is used for heating a hydrocarbon stream (c p = 2.0 kJ/kgK) steadily from 20C to 50C. A water stream enters the shellside at 80C and leaves at... Saturated water vapor at 100°C condenses in the shell side of a one-shell and two-tube heat exchanger with a surface area of 0.5 m 2 and an overall heat transfer coefficient of 2000 W/m 2... The condenser of a room air conditioner is designed to reject heat at a rate of 15,000 kJ/h from refrigerant-134a as the refrigerant is condensed at a temperature of 40°C. Air (c p = 1005... Which of the following reactions are allowed and which are forbidden by the conservation laws appropriate to weak interactions? (a) + + e + e ; (b) K + + + e + e ; (c) K + 0 + + + ;... Use the conservation of angular momentum and parity to determine possible angular momentum states in the reaction p + p + + and express the allowed transitions in spectroscopic notation for... Which of the following processes are allowed in electromagnetic interactions and which are allowed in weak interactions via the exchange of a single W or Z 0 ? (a) K + 0 + e + + e , (b) K + + +... Draw quark diagrams for the decays (a) D 0 K + + and (b) D 0 K + + . Estimate the ratio of their decay rates and compare this to the measured values. Show that the momentum for a 2-kg brick parachuting straight downward at a constant speed of 8 m/s is 16 kg m/s. Impulse = Ft Momentum = mv A race car rounds a curve at 60 m/s. The radius of the curve is 400 m, and the cars mass is 600 kg. (a) What is the cars (centripetal) acceleration? What is it in gs? (b) What is the centripetal... A 0.1-kg ball is attached to a string and whirled around in a circle overhead. The string breaks if the force on it exceeds 60 N. What is the maximum speed the ball can have when the radius of the... The energy emitted or absorbed in chemical processes is often quoted in kilo joules per mole (abbreviated mol) of reactants, where a mole contains N A 6.022 x 10 23 (Avogadros number) molecules (5).... Design a transmission system to carry power from wind farms in North Dakota to the state of Illinois (about 1200 km). The system should handle Illinoiss summer time electricity demand of 42GW. Land... A cylinder initially contains V 0 = 1 L of argon at temperature T 0 = 0 C and pressure p 0 = 1 atm. Suppose that the argon is somehow made to expand to a final volume V = 2 L in such a way that the... Consider a building with 3200 ft 2 of walls. Assume the ceiling is well-insulated and compute the energy loss through the walls based on the following materials, assuming an indoor temperature of 70... Show that the data in Table 9.6 satisfy the definitions of Gibbs and Helmholtz free energy, (1) ?G r =?H r ? T?S r and (2) ?H r = ?U r + p?V r . Quantity Value AUr Reaction internal energy +175.8... Air conditioners are rated by their Energy Efficiency Ratio, or EER, defined as the cooling power P r (in Btu/h), divided by the total electric power input P e (in watts), measured with T + = 95 F... Consider a throttled Otto cycle for an engine with the same parameters as Problem 11.1. In the throttled cycle assume that the spent fuelair mixture is ejected at 1 atm and brought in again at 0.5... The first radioactive element discovered by Polish physicist Marie Curie was radium-226. It has a halflife of 1700 years. Suppose you obtained a microgram of pure 226 Ra. How long would you have to... Check the quoted estimate of 4 10 9 tonnes of uranium from seawater quoted in this chapter. For how many years could this amount of uranium supply 100% of the worlds energy needs at the level of... An approximate description of the Oklo uranium deposit is 90% uraninite (UO 2 ) by mass, saturated with water that acted as the moderator. Assume that the Oklo deposit was homogeneously saturated... 131 I is a dangerous fission product because iodine is preferentially absorbed by the thyroid gland in children. It has a half-life of about 8 days and emits a -particle with average energy 180 keV.... Consider a location for a solar energy installation in Arizona, at latitude 34 . Compute the declination on the following dates: (i) March 20 (spring equinox),(ii) April 20. Compute the length of... Consider an idealized flat-plate solar collector with no conduction or convection losses, and with insolation 1000W/m 2 incident at an angle of 45 from the vertical. Assume that the collector is... The thickness of the germanium (density 5.32 gm/c m 3 ) layer in a triple-junction PV is typically greater than 100 microns. If the overall cell efficiency is 40%, how many watts of PV capacity... A large wind turbine blade is 50 m long and has a maximum chord length of 4 m at a point one-third of the way out from the wind turbine hub. When rotating at its design rate, the blade sees an air... Make a very rough estimate of the thermal energy content of Earth, assuming that the core has radius 3480 km, temperature 4000 K, density 11000 kg/m 3 and heat capacity 800 J/K kg, and that the rest... Consider the efficiency computed in the example single-flash cycle in Example 32.5. Use thermodynamic data on water to show that running the separator at T = 140 C or T = 160 C will decrease the... Although doubly charged baryons have been found (baryons with net charge 12), no doubly charged mesons have yet been identified. What effect on the quark model would there be if a meson of charge 12... Consider a house in a northern location that needs a total of 100 GJ of thermal energy over a winter season from November through March. Assume that the house has a ground source heat pump that... If you scuff electrons from your shoes while walking across a silk rug, are you negatively or positively charged? Two bunnies hop at slightly different rates but remain side by side. The first takes 50 hops per minute and the other takes 48 hops per minute. If they begin hopping together, when will they again be...
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