PMG Engineering | Build World-Class Food Factories | TechnicalGraphic | Heat transfer unit operations

Home / TechnicalGraphic / Heat transfer unit operations
Heat transfer unit operations
Heat transfer unit operations
IN FOOD PROCESSING Evaporation, drying, freezing, refrigeration, heat sterilization, pasteurization, and other food processing operations all involve heat transfer. Heat transfer is a dynamic process in which heat is transferred from one body to another that is cooler. Rate of heat transfer is determined by the temperature differences between the bodies; the greater the temperature difference, the greater the rate of heat transfer. Rate of heat transfer = temperature difference/ heat flow resistance of medium 3 ways of Heat Transfer 1. Conduction Heat transfer occurs due to the transfer of vibrational energy from one molecule to adjacent molecules in a solid mass. Conduction does not involve any physical movement of the body. Fourier's equation of heat transfer : dQ dT = - dT/dX 1/kA where, dQ/dT is conduction rate of heat transfer dT/dX is temp. difference/unit legth 1/kA is resistance offered by medium h is convective heat transfer coefficient A is area of cross section perpendicular to direction of heat flow k is thermal conductivity of body Ex; As heat is transferred from the meat to the cheese, cheese melts 2. Convection Heat tranfer occurs due to the movement of groups of molecules in a fluid. The groups of molecules can be moved by either density changes or forced fluid motion. The basic equation for the rate of convection heat transfer is known as Newton's Law of Cooling: Q conv = hA (T - Ts) where, Q˙conv is convective heat transfer rate h is convective heat transfer coefficient A is surface area of the object being cooled or heated, T∞ is bulk temperature of the surrounding fluid Ts is surface temperature of the object Ex; Boiling of Water Warm Molecules Cool Molecules 3. Radiation Transfer of heat energy by electromagnetic waves. Radiation operates independently of the medium in which it occurs. It's determined by the relative temperatures, geometric arrangements, and surface structures of the materials emitting or absorbing heat. Stefan-Boltzmann Law of heat transfer : q = A T 4 where, T is absolute temperature Sigma is stefan-boltzmann constant (5.670374419 × 10 -8 watt per square meter per kelvin) Ex; Baking in oven Radiation via resistors Heat Transfer Characteristics of Food Type of product Size of the container Agitation of the container Temperature of the retort Shape of the container. Type of container. Heat penetrates faster through metal than glass or plastics due to differences in thermal conductivity. Tall containers promote convection currents in convective heating foods.
Suggested Links
Questions?
Fill out the form below and we will get back to you within two business days.
Featured Product Categories
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Featured Technology Categories
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Featured Expertise Categories
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Featured Projects
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Articles
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Newsletters
Explore All
Filter Filter
Arrow
Arrow
Filters
✖
Thank you!
Your submission has been successfully sent.
Someone from our team will contact you soon.
Back to Top
Back to Top