TERMINOLOGY USED IN HVAC PART-5 Some common difinition used in hvac industry- SPECIFIC HEAT- The amount of heat necessary to change the temperature of a one pound of a substance 10F. SPECIFIC VOLUME- The volume of a substance per unit of mass; i,e standard air 13.33 cubic feet per pound. The reciprocal of density. STATE CONDITION- Substance can exist in three states; solid, liquid, and vapour. STATIC PRESURE- The normal force per unit area at a small hole in the wall of a duct. SUB COOLING- Cooling of a liquid, at a constant pressure, below the point at which it was condensed. SUBLIMATION- A condition where a substance changes from a solid to gas without becoming a liquid. SUCTION LINE- A tube used to convey the refrigerant vapour from the evaporator outlet to suction inlet of compressor. ACCUMULATOR- A device located in the suction line that intercepts quantity of a liquid refrigerant and thereby prevent damage to the compressor. SUPERHEAT- Heat added to a vapour after all li...
Posts
- Get link
- X
- Other Apps
TERMINOLOGY USED IN HVAC PART-4 Some common difinition used in hvac industry- REFRIGERANT- A substance which produce a refrigerating effect while expanding or vaporizing. REFRIGERANT CONTROL- A divice used to meter the amount of refrigerant to an evaporator. It also services as a dividing point betweem the high and low pressure side of the system. REFRIGERANT DISTRIBUTOR- A divice which meters equal quantities of refrigerant to independent circuits in the evaporator coil. REFRIGERANT MIGRATION- The movement of refrigerant through the system to the compressor crankcase during the off-cycle, caused by its attraction to coil. REFRIGERANT VELOCITY- The rate at which refrigerant is moving at a given point in a system, usually given in a feet per minute (FPM). REFRIGERATION- The transfer of heat from a place where it is not wanted to a place where its presence is not desirable. REFRIGERATION EFFECT- The amount of heat a given quantities of refrigerant will absorb in changing from a liq...
- Get link
- X
- Other Apps
TERMINOLOGY USED IN HVAC PART-3 Some common difinition used in hvac industry- FLASH GAS- Instantenious evaporation of some liquid refrigerant ar the metering divice temperature difference, the area exposed and the type of material. HEAT OF COMPRESSION- The heat added to a vapour by the work done during the compression. FREEZING POINT- The tempereture at which the removal of any heat will beging a change of state from a liquid to a solid. GAUGE PRESSURE- Pressure measured with atmospheric pressure as a base. HEAT- A form of energy causing the agitation of molicule within a substance. HEAT EXCHANGER- A device for the transfer of heat energy from the source to the conveying medium. HEAT FLOW- Heat flow from a warmer to a cooler substance. The rate depemds upon the refrigerant, Its expressed in BTU's. HEAT TRANSFER- There are three method of heat transfer are conduction, convection , radiation. LATENT HEAT- Heat that produces a change of state without a changing a temperature; ...
- Get link
- X
- Other Apps
TERMINOLOGY USED IN HVAC PART-2 Some common difinition used in hvac industry- CYCLE- The complete course of operation of a refrigerant back to a selected starting point in a system. Also used to discribe alternating current through 360 space degrees. DENSITY- Mass or weight per unit volume. For example, standard air = .75 pounds per cubic foot. DISCHARGE LINE- A tube used to convey the compressed refrigerant vapour from the compressor to condenser inlet. DISCHARGE PRESSURE- The pressure read at the compressure outlet. Also called head pressure or high pressureb side. DRY AIR- Air which contains no moixture vapour. DRY BULB TEMPERATURE- Temperature read with an ordinary thermometer. EFFECTIVE TEMPERATURE- An arbitary concept which combines into a single value the effect of temperature, humidity, and air movement as sensed by the human body. ENTHALPY- Total amount of heat in one pound of a substance calculated from accepted base, expressed in BTU's per poun...
- Get link
- X
- Other Apps
TERMINOLOGY USED IN HVAC PART-1 Some common difinition used in hvac industry- ABSOLUTE PRESSURE- Pressure measured with a base of zero. ABSOLUTE TEMPERATURE- A temperarure scale expressed in °F or °C using absolute zero as a base. Refered to as the Rankine or Kelvin Scale. ABSOLUTE HUMUDITY - The weight of water vapour in a given amount of air. Grain per cubic foot. AMBIENT - Refers to the temperature surrounding a body or units under test. AIR CONDITIONING- The process of controlling the temperature, humidity, cleanliness and distribution of the air. AIR STANDARD CONDITIONS- Conditions at which BTU ratings for summer air conditioning equpiment is rated. 95 °F dry bulb, 75 °F wet bulb at the condenser inlet and 80°F dry bulb, 67°F wet bulb at the evaporator inlet. ATMOSPHERIC PRESSURE - The weight of a 1 square inch column of the earth's atmospheric. At sea level this pressure is 14.696 pounds square inch (psi). B...
- Get link
- X
- Other Apps
MEHANICAL HVAC DESIGN ENGINEER'S RESPONSIBILITIES :- The normal procedure in a design-bid construction project and the mechanical engineer's responsibilities are- Initiation of a project by owner or developer. Organizing a design team. Determining the design criteria and indoor environmental parameters. Calculation of cooling and heating load. Selection of systems, subsystems, and their components. Preparation of schematic layout: sizing of piping and ductwork. Preparation of contract documents: drawing and specifications. Competitive bidding by various contractors; evaluation of bids; negotiations and modifications. Advice on awarding of contract. Monitoring, supervision, and inspection of installation; reviewing shop drawing. Supervision of commissioning. Modification of drawing to the as-built conditions; preparation of the operation and maintenance manual. Handing over to the property management for operation.
- Get link
- X
- Other Apps
INTERNATIONAL CODES & STANDARD :- The following international code & standard term are generally used in HVAC. ASHRAE : American Society of Heating, Refrigeration & Air conditioning Engineers. ARI : Air conditioning and Refrigeration Institutes. ASTM : American Society of Testing & Materials. NFPA : National Fire Protection Association. NEMA : National Environment Management Authority. SMACNA : Sheet Metal and Air conditioning Contractors National Association. UL : Underwrites Laboratories. OSHA : Occupational Safety and Health Administration. IAQ : Indoor Air Quality.