water. 11-78 A shell-and-tube heat exchanger with two shell passes and eight tube passes is used to heat ethyl alcohol (c₂=2670 J/kg-K) in the tubes from 25°C to 70°C at a rate of 2.1 kg/s. The heating is to be done by water (c=4190 J/kg-K) that enters the shell side at 95°C and leaves at 45°C. If the over- all heat transfer coefficient is 950 W/m².K, determine the heat transfer surface area of the heat exchanger. 70°C Ethyl alcohol 25°C 2.1 kg/s Water 95°C 45°C FIGURE P11-78 (8-tube passes)

Formaldehyde at 52.688 bar and 175.65 ℃ passes through a heater-expander and emerges at 39.516 bar and 420.45 ℃. There is no work into or out of the heater, but heat is supplied. Calculate the heat transfer into the heater-expander per mole of formaldehyde

1. A plastic (k = 0.5 W/m K) pipe carries a coolant at -35 °C with a heat-transfer coefficient of 300 W/m².K. The pipe ID is 3 cm and the OD is 4 cm. The exterior pipe surface is exposed to air at 25°C with a heat-transfer coefficient of 20 W/m²K. Radiative heat transfer may be neglected in this problem. (a) Calculate the rate of heat transfer to the coolant per meter of pipe length. (b) Calculate the temperature of the exterior pipe surface.

a cylinder-plunger contains 2.4x10 ^ -2 kg of air that is subjected to a cycle: Process 1-2: Isochoric process (0.02m ^ 3) from .1MPa to 0.42MPa Process 2-3: isobaric cooling Process 3-1: Isothermal heating Calculate Q and W for each stage

The air at 20 ° C and 60% RH is heated using a heat exchanger to reach 70 ° C. Using a psychrometric chart, determine a. The amount of heat added per 1 m³ of initial air = (kJ). b. Condensation temperature = (° C)

11.22 A shell-and-tube heat exchanger must be designed to heat 2.5 kg/s of water from 15 to 85°C. The heating is to be accomplished by passing hot engine oil, which is available at 160°C, through the shell side of the exchanger. The oil is known to provide an average convection coefficient of h, = 400 W/m² K on the outside of the tubes. Ten tubes pass the water through the shell. Each tube is thin walled, of diameter D = 25 mm, and makes eight passes through the shell. If the oil leaves the exchanger at 100°C, what is its flow rate? How long must the tubes be to accomplish the desired heating?

100 kg/s of a crude oil is heated from 24°C to 40°C through the tube side of a multitube heat exchanger. The crude oil flow is divided evenly among all 100 tubes in the tube bundle. The ID of each tube is 10 mm, and the inside tubewall temperature is maintained at 100°C. Average properties of the crude oil are p = 950 kg/m³, cp=1.9 kJ/kg-K, k= 0.25 W/m-K, μ = 12 mPa-s, and Uw = 4 mPa.s. Estimate the rate of heat transfer and the tube length. The rate of heat transfer is The tube length is m. W.

03: Air is contained in a vertical cylinder fitted with frictionless piston and a set of stops. The piston cross -sectional area is (0.2 m²) and the air inside is initially at (200 kPa, 500°C). The air is then cooled as a result of heat transfer to the surroundings. a) What is the temperature of the air inside the cylinder when the piston reaches the stops? b) The cooling is now contained until the temperature reaches (20°C), what is the pressure at this state? Ans. [a) 113.4 °C, b) 151.7 kPa] Air 0.25 0.25

A stream of ammonia is cooled from 100oC to 20oC at a rate of 180 kg/hr in the tube side of a double-pipe counter-flow heat exchanger. Water enters the heat exchanger at 10oC at a rate of 250 kg/hr. The outside diameter of the inner tube is 3 cm and the length of the pipe is 7m. Using the log-mean temperature difference, calculate the overall heat transfer coefficient (U) for the heat exchanger. Determine the heat transfer rate between the two fluids. Determine the outlet temperature of the water. Determine the heat transfer surface area. Determine the log-mean temperature difference. Determine the heat transfer coefficient for the heat exchanger.   Cp for ammonia is 5234J/kgK and cp for water is 4180J/kgK.