Question

. [Problem 11-5, p.689 in Bergman, et al.] The condenser of a steam power plant contains N = 1000 brass tubes (k = 110 W/m-K), each of inner and outer diameters, D1 = 25 mm and D2 = 28 mm respectively. Steam condensation on the outer surfaces of the tubes is characterized by a convection coefficient of ho = 10,000 W/m2-K. (a) If cooling water from a large lake is pumped through the condenser tubes at ṁw = 400 g/s, what is the overall heat transfer coefficient Uo (based upon the outer surface of the tube)? Properties of the water may be approximated as μ = 9.60x10‒4 N-s/m2, k = 0.60 W/m-K, and Pr = 6.6. You may use eqn.(8.60): hi = 0.023 (k/D1) ReD4/5 Pr0.4. (b) If, after extended operation, fouling provides a resistance of Rf = 10‒4 m2-K/W, at the inner surface, what is the value of Uo? (c) If water is extracted from the lake at 15 oC and 10 kg/s of steam at 0.0622 bars are to be condensed, what is the corresponding temperature of the water leaving the condenser? The specific heat of water is 4.180 kJ/kg-K and the heat of vaporization of the steam is 2414 kJ/kg. You may assume that ReD for the water = 3400

Answer #1

The condenser of a large steam power plant is a heat exchanger
in which steam is condensed to liquid water. Assume the condenser
to be a parallel flow shell-and-tube heat exchanger consisting of a
single shell and 10,000 tubes, each executing two passes. The tubes
are of thin wall construction with D = 30 mm and the steam
condenses on their outer surface. The heat transfer rate that must
be effected by the exchanger is Q = 2 × 10^9...

An air-cooled steam condenser is operated with air in cross flow
over a square, in-line array of 400 tubes (NL=NT= 20), with an
outside tube diameter of 20 mm and longitudinal and transverse
pitches of SL= 60 mm and ST= 42 mm, respectively. Saturated steam
at a pressure of 2.455 bars enters the tubes, and a uniform tube
outer surface temperature of Ts= 390 K may be assumed to be
maintained as condensation occurs within the tubes.
(a) If the...

Steam at an average temperature of ?∞= 400°C flows through a
steel pipe. The inner and outer radii of the pipe are r1 = 4 cm and
r2 = 4.5 cm, respectively, and the outer surface of the pipe is
insulated with a layer of 50 mm thick-calcium silicate of thermal
conductivity of k = 0.5 W/m.K, and is maintained at 350 °C. If the
convection heat transfer coefficient on the inner surface of the
pipe is h = 65...

Water at a flow rate of 60 kg/s enters the shell-side
of a baffled shell-and-tube heat exchanger at 35 °C and leaves at
25 °C. The heat will be transferred to 150 kg/s of raw water coming
from a supply at 15 °C. You are requested to design the heat
exchanger for this purpose. A single shell and single tube pass is
preferable. The tube diameter is ¾ in. (19 mm outer diameter with
16 mm inner diameter) and tubes...

Saturated water vapor leaves a steam turbine at a flow rate of
1.47 kg/s and a pressure of 0.51 bar. The vapor is to be completely
condensed to saturated liquid in a shell-and-tube heat exchanger
that uses city water as the cold fluid. The water enters the
thin-walled tubes at 17oC and is to leave at 57.6
oC. Assuming an overall heat transfer coefficient of
2000 W/m2K, determine the required heat exchanger
surface area and the water flow rate. cp,c...

Consider an R-134a based freezer operating at -30°C. The
surrounding temperature is at 25°C. External size of the freezer is
33.62" wide x 37.37" tall x 20.68" deep. Wall thickness of the
freezer is 1" and made of polystyrene (thermal conductivity=.033
W/mK). Thermal conductivity of the wall is the same as polystyrene.
For simplicity, you may assume the inner and outer convection
coefficients of the freezer are both equal to 10 W/m2/K.
The heat removal rate is: q(convection)=186.22 W
The...

water at the rate of 225 kg/hours is to be heated from
350C to 950C by means of a concentric tube
heat exchanger. Oil at a rate of 225kg/hr with specific heat of
2095 J/kg.K and temperature of 2100C is to be used as
the hot fluid. If the overall heat transfer coefficient based on
the outer diameter of the inner tube is 550 W/m2.K,
determine the length of heat exchanger if the outer diameter of the
tube is 100...

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (?a = 0.3 · 10?6
m2/s, cpa...

(a) Fluid at a mass flow rate of 0.352 kg/s flows through a tube
with a diameter of 15 mm and a length of 25 m. The inner surface of
the tube is heated with a uniform heat flux of 1000 W/m2.
Measurements shown that the inlet temperature of the fluid is 30
˚C. Assume the outer surface of the tube is perfectly insulated.
Consider the thermophysical properties of the fluid are as follows:
density ρ = 1000 kg/m3, specific...

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (va = 0.3 ·
10-6m2/s, cpa =...

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