Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 6, Problem 6.84P
An experiment is conducted to determine the average 
- Calculate the average mass transfer convection coefficient based on the wetted area during the evaporation process when the droplet, heater, and the dry ambient air are at
- How much energy will be required to evaporate the droplet if the dry ambient air temperature is
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In a falling-film evaporator, Air at 40℃ and 50 kPa flows through a wetted-wall column with 100 mm diameter at a velocity of 5 m/s. What is the mass-transfer coefficient for the humidification of this stream by evaporation from the wet walls? If the air in this situation is 50 % saturated, and the saturation particle pressure of water vapour at 40℃ is 7375 Pa, what is the local evaporation flux in a unit of kg/m²s?
Air at 25°C and atmospheric pressure flows with a velocity of 3 m/s inside a 10mm diameter tube of 1 m length. The inside surface of the tube contains a deposit of naphthalene. Determine the average mass transfer coefficient for the transfer of naphthalene from the pipe surface into the air.
(a) Derive an expression for the saturation vapour pressure of water in equilibrium with its vapour
under the assumptions that the latent heat of vaporisation is temperature independent, that the vapour
can be treated as an ideal gas and that the volume occupied by the vapour is much_greater than the.
volume occupied by the liquid.
(b) Calculate the relative humidity (in %) for an air temperature of 24 °C and dew point temperature
of 20 °C. (The saturation vapour pressure at 0 °C is 611 Pa, the specific gas constant for water vapour
is 461.5 J kg' K and latent heat of vaporisation of water is 2.5 x 10° J kg).
Chapter 6 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 6 - The temperature distribution within a laminar...Ch. 6 - In flow over a surface, velocity and temperature...Ch. 6 - In a particular application involving airflow over...Ch. 6 - Water at a temperature of T=25C flows over one of...Ch. 6 - For laminar flow over a flat plate, the local heat...Ch. 6 - A flat plate is of planar dimension 1m0.75m. For...Ch. 6 - Parallel flow of atmospheric air over a flat plate...Ch. 6 - For laminar free convection from a heated vertical...Ch. 6 - A circular. hot gas jet at T is directed normal to...Ch. 6 - Experiments have been conducted to determine local...
Ch. 6 - A concentrating solar collector consists of a...Ch. 6 - Air at a free stream temperature of T=20C is in...Ch. 6 - The heat transfer rate per unit width (normal to...Ch. 6 - Experiments to determine the local convection heat...Ch. 6 - An experimental procedure for validating results...Ch. 6 - If laminar flow is induced at the surface of a...Ch. 6 - Consider the rotating disk of Problem 6.16. A...Ch. 6 - Consider airflow over a flat plate of length L=1m...Ch. 6 - A fan that can provide air speeds up to 50 m/s is...Ch. 6 - Consider the flow conditions of Example 6.4 for...Ch. 6 - Assuming a transition Reynolds number of 5105,...Ch. 6 - To a good approximation, the dynamic viscosity the...Ch. 6 - Prob. 6.23PCh. 6 - Consider a laminar boundary layer developing over...Ch. 6 - Consider a laminar boundary layer developing over...Ch. 6 - Experiments have shown that the transition from...Ch. 6 - An object of irregular shape has a characteristic...Ch. 6 - Experiments have shown that, for airflow at T=35C...Ch. 6 - Experimental measurements of the convection heat...Ch. 6 - To assess the efficacy of different liquids for...Ch. 6 - Gases are often used instead of liquids to cool...Ch. 6 - Experimental results for heat transfer over a flat...Ch. 6 - Consider conditions for which a fluid with a free...Ch. 6 - Consider the nanofluid of Example 2.2. Calculate...Ch. 6 - For flow over a flat plate of length L, the local...Ch. 6 - For laminar boundary layer flow over a flat plate...Ch. 6 - Sketch the variation of the velocity and thermal...Ch. 6 - Consider parallel flow over a flat plate for air...Ch. 6 - Forced air at T=25C and V=10m/s is used to cool...Ch. 6 - Consider the electronic elements that are cooled...Ch. 6 - Consider the chip on the circuit board of Problem...Ch. 6 - A major contributor to product defects in...Ch. 6 - A microscale detector monitors a steady flow...Ch. 6 - A thin, flat plate that is 0.2m0.2m on a side is...Ch. 6 - Atmospheric air is in parallel flow...Ch. 6 - Determine the drag force imparted to the top...Ch. 6 - For flow over a flat plate with an extremely rough...Ch. 6 - A thin, flat plate that is 0.2m0.2m on a side with...Ch. 6 - As a means of preventing ice formation on the...Ch. 6 - A circuit board with a dense distribution of...Ch. 6 - On a summer day the air temperature is 27C and the...Ch. 6 - It is observed that a 230-mm-diameter pan of water...Ch. 6 - The rate at which water is lost because of...Ch. 6 - Photosynthesis, as it occurs in the leaves of a...Ch. 6 - Species A is evaporating from a flat surface into...Ch. 6 - Prob. 6.57PCh. 6 - Prob. 6.58PCh. 6 - An object of irregular shape has a characteristic...Ch. 6 - Prob. 6.60PCh. 6 - An object of irregular shape 1 m long maintained...Ch. 6 - Prob. 6.62PCh. 6 - Prob. 6.63PCh. 6 - Prob. 6.64PCh. 6 - Prob. 6.65PCh. 6 - A streamlined strut supporting a bearing housing...Ch. 6 - Prob. 6.67PCh. 6 - Consider the conditions of Problem 6.7, for which...Ch. 6 - Using the naphthalene sublimation technique. the...Ch. 6 - Prob. 6.70PCh. 6 - Prob. 6.71PCh. 6 - Prob. 6.72PCh. 6 - Dry air at 32C flows over a wetted (water) plate...Ch. 6 - Dry air at 32C flows over a wetted plate of length...Ch. 6 - Prob. 6.75PCh. 6 - Prob. 6.76PCh. 6 - Prob. 6.77PCh. 6 - An expression for the actual water vapor partial...Ch. 6 - A mist cooler is used to provide relief for a...Ch. 6 - A wet-bulb thermometer consists of a...Ch. 6 - Prob. 6.81PCh. 6 - Prob. 6.83PCh. 6 - An experiment is conducted to determine the...Ch. 6 - Prob. 6.85PCh. 6 - Consider the control volume shown for the special...Ch. 6 - Prob. 6S.2PCh. 6 - Prob. 6S.3PCh. 6 - Consider two large (infinite) parallel plates, 5...Ch. 6 - Prob. 6S.5PCh. 6 - Consider Couette flow for which the moving plate...Ch. 6 - A shaft with a diameter of 100 mm rotates at 9000...Ch. 6 - Consider the problem of steady, incompressible...Ch. 6 - Prob. 6S.11PCh. 6 - A simple scheme for desalination involves...Ch. 6 - Consider the conservation equations (6S.24) and...
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- large dry air is flowing over a surface from which benzene is evaporating with 1 atm absolute pressure as total pressure. The partial pressure of benzene at the surface is the vapor pressure at 298 K which is (0.42 atm). The Ke has been estimated to be (6.5*10s kmol / s.m'. mol vol.). Calculate the vaporizing rate benzene, and the individual mass transfer coefficient Ky? (R=0.000082)arrow_forwardFrom an open water surface with air temperature 22°C, relative humidity is 40% and wind speed is 3 m/s, all measured at height 2 m above the water surface. Assume a roughness height of 0.03 cm. The net radiation is 200 W/m^2. Cp = 1005 J/kg-K A. Calculate the latent heat of vaporization (J/kg) B. Calculate the evaporation using Energy Balance Method (mm/day) C. Calculate the saturation deficit of the vapor pressure (Pa) D. Calculate the evaporation using Priestley-Taylor Method (mm/day)arrow_forwardA moist cement omnes diameter 10 ohm circular cross-section will be dried using air in a tray and, for example, the variation of moisture content over time will be examined. The heat transfer coefficient was calculated as 0.68 cal/min.cm³.C in the fixed still drying arab. Dry and wet chamber temperatures of the air used for drying are 35 and 20°C, respectively. For example, calculate the mass transfer coefficient during the 10-minute constant speed drying interval. (Note: the humidity of the air (Ha) should be calculated with the humidity diagram.) Data Evaporation enthalpy of water: 2454.2 kj/kg at 20°C 2418.6 k/kg at 35C Vapor pressure of water: 17.54 mm Hg at 20°C. 35C is 42.18 mm Hg.arrow_forward
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