Studies in heat and mass transfer

Cleland, Daniel (1961) Studies in heat and mass transfer. PhD thesis, University of Glasgow.

Abstract

The previous experimental and theoretical work on the relationships between the rates of heat and mass transfer was reviewed. Experimental work was conducted in order to accumulate sufficient data on the system of a gas flowing over an object of rectangular cross-section so that the rates of heat transfer, mass transfer, might be related to the flow characteristics of the system, expressed in terms of the Reynolds group. The experimental work was carried out in a pilot plant continuous fibre drier. The fibre, moving through the drier, becomes compressed into the form of a continuous slab of rectangular section. In the drier, the air flows at right angles to one of the two larger surfaces of the fibre tow, giving the system desired. Water was evaporated from the fibre tow and the rates of heat and mass transfer measured during the constant rate period of drying over a wide range of air conditions. The following equations were used to correlate the results, In order to investigate the effect of the Schmidt group, liquids of varying physical properties, were evaporated from the fibre tow, the experiments being similar to those carried out with water. The results were correlated by the following equations, The rates of heat and mass transfer wore compared using j factors and jd/jh was found to be 1.05. The drying characteristics of a continuous fibre drier were also investigated and the rate of drying during the constant rate period was found to be given by, No method was found of predicting the critical moisture content under varying air conditions. The factors influencing the rate of drying during the falling rate period were also investigated and diffusion was found to be the controlling factor in the drying of fibre tows. Investigations into the falling rate period were carried out by comparing the drying curve to that for diffusion from a porous slab. The time taken for the fibre to dry from the critical moisture content Wo to some other value of moisture content (W) is given by the equation The diffusion coefficient, DF, was found to be influenced by tomperature, humidity, and air velocity. The effect of velocity was found to be related to the diffusion coefficient by the relationship, However the effects of temperature and humidity could not be expressed in mathematical terms. In order to obtain the relationship for the falling rate period, the equilibrium moisture contents over a wide range of ambient air conditions wore measured.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: C GM Slesser
• Keywords: Thermodynamics
• Date of Award: 1961
• Depositing User: Enlighten Team
• Unique ID: glathesis:1961-73495
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73495