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:

ok yeah for me again

explanation:

Answer from: Quest

hes mad if he says,

explanation:

Another question on Engineering

Engineering, 03.07.2019 14:10

If the thermal strain developed in polyimide film during deposition is given as 0.0044. assume room temperature is kept at 17.3 c, and thermal coefficient of expansion for the film and the substrate are 54 x 10^-6c^-1 and 3.3 x 10^-6c^-1respectively. calculate the deposition temperature.

Answers: 3

Answer

Engineering, 04.07.2019 18:20

Avolume of 2.65 m3 of air in a rigid, insulated container fitted with a paddle wheel is initially at 264 k, 5.6 bar. the air receives 432 kj by work from the paddle wheel. assuming the ideal gas model with cv = 0.71 kj/kg • k, determine for the air the amount of entropy produced, in kj/k

Answers: 2

Answer

Engineering, 04.07.2019 18:20

Aheavily insulated piston-cylinder device contains 0.02 m3 of steam at 300 kpa and 200 °c. 1.2 mpa. d this process. team is now compressed in a reversible manner to a pressure of etermine the entropy change and the work done on the steam during this process

Answers: 1

Answer

Engineering, 04.07.2019 19:10

Asteam is contained in a rigid tank with a volume of 1 m3. initially, the pressure and temperature are 7 bar and 500 oc, respectively. the temperature drops due to cooling process. determine: (1) the temperature at which condensation begins in °c, (2) the fraction of the total mass that has condensed when the pressure decreased to 0.5 bar. (3) the volume in m3 occupied by saturated liquid at the final state?

Answers: 3

Answer

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...

Questions