Engineering, 11.06.2020 20:57 wilwhe3231

A shell-and tube heat exchanger (two shells, four tube passes) is used to heat 10,000 kg/h of pressurized water from 35 to 120 oC with 5000 kg/h pressurized water entering the exchanger at 300 oC. If the overall heat transfer coefficient is 1500 W/m^2-K, determine the required heat exchanger area.

Answers: 1

Show answers

Answers

Answer from: hope10079

4.75m^2

Explanation:

Given:-

- Temperature of hot fluid at inlet: T_h_i = 300 °C

- Temperature of cold fluid at outlet: T_c_o = 120 °C

- Temperature of cold fluid at inlet: T_c_i = 35 °C

- The overall heat transfer coefficient: U = 1500 W / m^2 K

- The flow rate of cold fluid: m_c = 10,00 kg/ h

- The flow rate of hot fluid: m_h = 5,000 kg/h

Solution:-

- We will evaluate water properties at median temperatures of each fluid using table A-4.

Cold fluid: Tci = 35°C , Tco = 35°C

Tcm = 77.5 °C ≈ 350 K --- > $C_p_c = 4195 \frac{J}{kg.K}$

Hot fluid: Thi = 300°C , Tho = 150°C ( assumed )

Thm = 225 °C ≈ 500 K --- > $C_p_h = 4660 \frac{J}{kg.K}$

- We will use logarithmic - mean temperature rate equation as follows:

$A_s = \frac{q}{U*dT_l_m}$

Where,

A_s : The surface area of heat exchange

ΔT_lm: the logarithmic differential mean temperature

q: The rate of heat transfer

- Apply the energy balance on cold fluid as follows:

$q = m_c * C_p_c * ( T_c_o - T_c_i )\\\\q = \frac{10,000}{3600} * 4195 * ( 120 - 35 )\\\\q = 9.905*10^5 W$

- Similarly, apply the heat balance on hot fluid and evaluate the outlet temperature ( Tho ) :

$T_h_o = T_h_i - \frac{q}{m_h * C_p_h} \\\\T_h_o = 300 - \frac{9.905*10^5}{\frac{5000}{3600} * 4660} \\\\T_h_o = 147 C$

- We will use the experimental results of counter flow ( unmixed - unmixed ) plotted as figure ( Fig . 11.11 ) of the " The fundamentals to heat transfer" and determine the value of ( P , R , F ).

- So the relations from the figure 11.11 are:

$P = \frac{T_c_o - T_c_i}{T_h_i - T_c_i} \\\\P = \frac{120 - 35}{300 - 35} \\\\P = 0.32$

$R = \frac{T_h_i - T_h_o}{T_c_o - T_c_i} \\\\R = \frac{300 - 147}{120 - 35} \\\\R = 1.8$

Therefore, P = 0.32 , R = 1.8 ---- > F ≈ 0.97

- The log-mean temperature ( ΔT_lm - cf ) for counter-flow heat exchange can be determined from the relation:

$dT_l_m = \frac{( T_h_i - T_c_o ) - ( T_h_o - T_c_i ) }{Ln ( \frac{( T_h_i - T_c_o )}{( T_h_o - T_c_i )} ) } \\\\dT_l_m = \frac{( 300 - 120 ) - ( 147 - 35 ) }{Ln ( \frac{( 300-120 )}{( 147-35)} ) } \\\\dT_l_m = 143.3 K$

- The log - mean differential temperature for counter flow is multiplied by the factor of ( F ) to get the standardized value of log - mean differential temperature:

dT_l = F*dT_l_m = 0.97*143.3 = 139 K

- The required heat exchange area ( A_s ) can now be calculated:

$A_s = \frac{9.905*10^5 }{1500*139} \\\\A_s = 4.75 m^2$

Answer from: Quest

answer:

look in settings

explanation:

Answer from: Quest

answer:

uygtfjyftujtfj

explanation:

Other questions on the subject: Engineering

Engineering, 04.07.2019 18:10, mm016281

What difference(s) did you notice using a pneumatic circuit over hydraulic circuit. explain why the pneumatic piston stumbles when it hits an obstacle.

Answers: 2

continue

Engineering, 04.07.2019 18:10, viicborella

Steel is coated with a thin layer of ceramic to protect against corrosion. what do you expect to happen to the coating when the temperature of the steel is increased significantly? explain.

Answers: 1

continue

Engineering, 04.07.2019 18:10, ashleybaber4966

If a particle moves along a path such that r : (3 sin t) m and ? : 2t rad, where t is in seconds. what is the particle's acceleration in m/s in 4 seconds? a)- 16.43 b)- 16.29 c)- 15.21 d)- 13.79

Answers: 1

continue

Engineering, 04.07.2019 18:10, ijohnh14

Shafts are machine elements that are used to a) carry axial loads b) direct shear loads c) transmit power d) rotate at constant speed e) none of the above circular and square shafts subjected to the same torque under the same circum behave a) the same way b) almost the same way

Answers: 2

continue

You know the right answer?

A shell-and tube heat exchanger (two shells, four tube passes) is used to heat 10,000 kg/h of pressu...