Explanation Express initial partial pressure. P ν 1 = ϕ 1 P g 1 = ϕ 1 P sat@93°F (I) Here, relative humidity at state 1 is ϕ 1 , initial water vapor pressure is P g 1 and saturation pressure at temperature of 93°F is P sat@93°F . Express initial specific humidity. ω 1 = 0.622 P ν 1 P 1 − P ν 1 (II) Here, pressure at state 1 is P 1 . Express initial enthalpy. h 1 = c p T 1 + ω 1 h g 1 @ 93 °F (III) Here, initial specific enthalpy at saturated vapor and temperature of 93°F is h g 1 @ 93 °F , specific heat at constant pressure of air is c p and temperature at state 1 is T 1 . Let the liquid water is supplied at a temperature almost equal to the exit temperature of the air stream, thus the evaporative cooling process travels through line of constant wet-bulb temperature, that is almost parallel to constant enthalpy lines. Thus, the enthalpy at state 1 and 2 is almost equal. h 2 ≅ h 1 (IV) Here, enthalpy at state 2 is h 2 . Express final specific humidity. ω 2 = 0.622 P g 2 P 2 − P g 2 (V) Here, pressure at state 2 is P 2 and final water vapor pressure is P g 2 . Express the exit temperature. h 2 = c p T 2 + ω 2 ( 1060.9 + 0.435 T 2 ) (VI) Here, exit temperature is T 2 . Conclusion: Refer Table A-4E, “saturated water-temperature table”, and write saturation pressure at temperature of 93°F using an interpolation method. Write the formula of interpolation method of two variables. y 2 = ( x 2 − x 1 ) ( y 3 − y 1 ) ( x 3 − x 1 ) + y 1 (VII) Here, the variables denote by x and y is temperature and saturation pressure respectively. Show the saturation pressure corresponding to temperature as in Table (1). Temperature T ( ° F ) Saturation pressure P sat ( psia ) 90 ( x 1 ) 0.6990 ( y 1 ) 93 ( x 2 ) ( y 2 = ? ) 95 ( x 3 ) 0.8164 ( y 3 ) Substitute 90°F,93°F and 95°F for x 1 , x 2 and x 3 respectively, 0 .6990 psia for y 1 and 0.8164 psia for y 3 in Equation (VII). y 2 = ( 93°F − 90°F ) ( 0.8164 psia − 0 .6990 psia ) ( 95°F − 90°F ) + 0 .6990 psia = 0 .7676 psia = P sat@93°F Substitute 0.30 for ϕ 1 and 0 .7676 psia for P sat@93°F in Equation (I). P ν 1 = ( 0.30 ) ( 0 .7676 psia ) = 0.230 psia Substitute 0 .230 psia for P ν 1 and 14

9th Edition

ISBN: 8220106796979

Author: CENGEL

Publisher: YUZU

See similar textbooks

Videos

Question

Chapter 14.7, Problem 93P

To determine

The exit temperature of air.

Expert Solution & Answer

Want to see the full answer?

Check out a sample textbook solution

See solution

Chapter 14.7, Problem 92P

Chapter 14.7, Problem 94P

Students have asked these similar questions

Distilled water is being cooled by a 20% propylene glycol solution in a 1-1/U counter flow plate and frame heat exchanger. The water enters the heat exchanger at 50°F at a flow rate of 86,000 lbm/h. For safety reasons, the water outlet temperature should never be colder than 35°F. The propylene glycol solution enters the heat exchanger at 28°F with a flow rate of 73,000 lbm/h. The port distances on the heat exchanger are Lv = 35 in and Lh = 18 in. The plate width is Lw = 21.5 2 in. The plate thickness is 0.04 in with a plate pitch of 0.12 in. The chevron angle is 30° and the plate enlargement factor is 1.17. All ports have a 2 in diameter. The fouling factor of the propylene glycol solution can be estimated as 2 ×10−5 h-ft2-°F/Btu. a. Determine the maximum number of plates the heat exchanger can have while ensuring that the water outlet temperature never drops below 35°F. b. Determine the thermal and hydraulic performance of the heat exchanger with the specified number of plates.…

Liquid pentane is flowing in the shell of a shell and tube heat exchanger at a rate of 350,000lbm/hr and an average temperature of 20°F. The shell has a diameter of 27 in and a length of 16ft. The tubes in the heat exchanger are ¾-in 15 BWG tubes on a 1-in triangular pitch. The purposeof this problem is to investigate how the number of baffles impacts the heat transfer and thepressure drop on the shell side of the heat exchanger. Calculate the shell-side convective heattransfer coefficient and pressure drop for the case where the heat exchanger has 10 baffles. Repeatthe calculation for 20 baffles. Then determine thea. Ratio of the shell-side convective heat transfer coefficient for the 20-baffle heat exchangerto the 10-baffle heat exchangerb. Ratio of the shell-side pressure drop for the 20-baffle heat exchanger to the 10-baffle heatexchangerc. If the optimum baffle spacing is somewhere between 0.4Ds and 0.6Ds, how many baffleswould you recommend for this heat exchanger? What are the…

The evaporator of a vapor compression refrigeration cycle utilizing R-123 as the refrigerant isbeing used to chill water. The evaporator is a shell and tube heat exchanger with the water flowingthrough the tubes. The water enters the heat exchanger at a temperature of 54°F. The approachtemperature difference of the evaporator is 3°R. The evaporating pressure of the refrigeration cycleis 4.8 psia and the condensing pressure is 75 psia. The refrigerant is flowing through the cycle witha flow rate of 18,000 lbm/hr. The R-123 leaves the evaporator as a saturated vapor and leaves thecondenser as a saturated liquid. Determine the following:a. The outlet temperature of the chilled waterb. The volumetric flow rate of the chilled water (gpm)c. The UA product of the evaporator (Btu/h-°F)d. The heat transfer rate between the refrigerant and the water (tons)

Chapter 14 Solutions

EBK THERMODYNAMICS: AN ENGINEERING APPR

Ch. 14.7 - What is the difference between dry air and...Ch. 14.7 - What is vapor pressure?Ch. 14.7 - What is the difference between the specific...Ch. 14.7 - Can the water vapor in air be treated as an ideal...Ch. 14.7 - Explain how vapor pressure of the ambient air is...Ch. 14.7 - Is the relative humidity of saturated air...Ch. 14.7 - Moist air is passed through a cooling section...Ch. 14.7 - How will (a) the specific humidity and (b) the...Ch. 14.7 - Prob. 9P Ch. 14.7 - Consider a tank that contains moist air at 3 atm...

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.

The exit temperature of air.

Solution Summary: The author analyzes the evaporative cooling process, which travels through line of constant wet-bulb temperature parallel to constant enthalpy lines.

Videos

The exit temperature of air.

Want to see the full answer?

Chapter 14 Solutions