Midterm

 is a branch of science that deals with the process of cooling of a space or substance below the environmental temperature.

is an assembly of four major components, namely, the compressor, condenser, expansion valve and the evaporator through which a very low boiling point substance flow in a cycle and absorbs heat from the immediate surroundings, thereby producing the cooling effect.

is a sequence of thermodynamic processes whereby heat is withdrawn from a cold body and expelled to a hot body

Cp of air

cause food spoilage, are controlled by low temperature.

enzymes are destroyed by

are found in fresh foods. They are tiny particles in meat, fish and poultry. If they are abuse in any way, such as cell disruption (breaking), the food quickly becomes rancid.

in food forms ice crystals when frozen. Fast freezing produces small ice crystals; slow freezing allows twice for larger crystal growth.

is an organized method of holding and protecting articles or commodities for future used, dates from earlier times when it was involved in the preservation of agricultural products,

 is increased by color change of food, though food value is not affected.

is usually associated with retail establishments where rapid turnover of the product is normally expected.

is usually carried out by wholesalers and commercial storage warehouses. The storage period depends on the type of product stored and on the condition of the product in entering storage.

requires freezing of the product and storage at some temperature between 10°F and -10°F, with 0°F being the temperature most frequently employed.

It is the heat that must be removed from the refrigerated product in

order to reduce the temperature of the product to the desired level

1.65 Btu/hr. ft.2 °F

6.0 Btu/hr.ft2. °F

the process of removing moisture in varying amounts of water from solid or semi-solid materials.

usually removed from the material and the drying chamber by using an

are substances which are, particularly, variable in the

moisture content which they can possess at different times.

or dry weight, is the content weight reached by hygroscopic

substance after being dried out, or removal of all moisture content.

 is the hygroscopic moisture content of a substance expressed as a

percentage of the bone-dry weight of the material.

is expressed as a percentage of the gross weight of the body, and

 may refer to both hygroscopic and purdy surface substance

removes or reduces only a portion of the surface moisture. It

can be done by pressure, by suction, or by decantation

this method will not only reduce or remove the surface liquid but

will also remove internal moisture and in many cases water in chemical

combination. Inherent or bed moisture are other terms for internal

moisture.

may have the flame from combustion impinging on the material being dried, or gases of combustion may be mixed with air to reduce temperature.

has the gases of combustion pass through spaces surrounding, or in other ways, heating the drying chamber, but the gases are allowed in contact with the material being dried at any time.

has the material in contact with steam pipes or the air is passed over steam heaters and then over or through the material being dried.

is the most commonly used dryer, consisting of a rotating cylinder inside which the material flow while in contact with hot gases, either parallel or counterflow. The cylinder is tilted at a slight angle and filled with lifting flights.

where hot gases from combustion chamber or heated air from steam heaters, is in direct contact with the material being dried (either parallel or counterflow)

are vertical shafts connected at the bottom to some source of heat. The wet material is introduced at the top and falls downward over baffles installed in the shaft and at the same time comes in contact with the hot air or gases which rise and exhaust at the top of the stack. This is usually made without any moving parts except any required by heat source. The draft is fixed by the tower or shaft design and the flow of material is by gravity. This type is used for drying palay, wheat, grains, etc.

are used for materials requiring careful handling, no agitation and require slow drying

is a type of dryer in which the material to be dried is supported on a floor or hearth made of brick, steel, or other materials hearth made of brick, steel, or other materials and receives its heat through such floor or hearth.

 is one of the latest type of dryers. Heat comes from the banks of infrared lamps with reflecting bowl directing the infrared rays towards the material to be dried.

has been used for drying wheat and wood flours, chemical salts, spent grains, sewage sludge, and for secondary drying of small sizes of coal.