loggg

http://www.hvac-calculator.net/

Handling Equipment (Eq. Elements)

Fan

 You need to determinate flow rate and blower pressure (optional to account the influence of fan energy).

Required Input data:

            Air flow rate.

Optional Input data:

Fan total pressure .

----------------------------------------------------------------------------------------------------------------------

MixBox

 Recirculation air connection cell (mixing chamber).

Required Input data:

            recirculation flow rate (cfm or m3/h) OR recirculation percentage.

Optional Input:

            Temperature and humidity ratio, if it is NOT equal to inside parameters.

---------------------------------------------------------------------------------------------------------------------- 

Cooling Coil

AIR-cooling coils are used for air cooling with or without accompanying dehumidification.

A dehumidifying coil normally removes both moisture and sensible heat from entering air. In most air-conditioning processes, the air to be cooled is a mixture of water vapor and dry air gases. Both lose sensible heat when in contact with a surface cooler than the air. The removal of latent heat through condensation occurs only on the portions of the coil where the surface temperature is lower than the dew-point of the air passing over it.

When the coil starts to remove moisture, the cooling surfaces carry both the sensible and latent heat load. Cooling coil can use chilled water or refrigerant as direct expansion system.

The dry-bulb, wet-bulb temperature, enthalpy are decreased, the relative humidity is increased.

            Optional Input:

Chilled water supply and return temperatures ( t1w and t2w ) .

 ----------------------------------------------------------------------------------------------------------------------

Heating Coil

 Air heating coils are used to heat air under forced convection.

The total coil surface may consist of a single coil section or several coil sections assembled into a bank. The coils apply primarily to air conditioning using steam, hot water, refrigerant vapor heat reclaim, and electricity.

Important features of a sensible heating process:

This  process takes place at constant humidity ratio: the humidity ratio, vapor pressure and dew-point remain are unchanged,

The dry-bulb, wet-bulb temperature, enthalpy are increased,

The relative humidity is decreased.

            Optional Input:

Hot water supply and return temperatures ( t1w and t2w ) 

----------------------------------------------------------------------------------------------------------------------

Adiabatic humidification

 It is a constant enthalpy process and air decreases its temperature.

The psychrometric state point of the leaving air is on the constant thermodynamic wet-bulb temperature line with its end state determined by the saturation effectiveness of the device.

Fogging systems use compressed air to atomize water and create a stream of microscopic water particles, which appears as fog. The water particles quickly change from liquid to gas as they absorb heat from the air stream.

Spray-type air washers consist of a chamber or casing containing spray nozzles, a tank for collecting spray water as it falls, and an eliminator section for removing entrained drops of water from the air. A pump recirculates water at a rate higher than the evaporation rate. Intimate contact between the spray water and the air causes heat and mass transfer between the air and the water.  Except for the small amount of energy added by the recirculating pump and the small amount of heat leakage into or from the apparatus (including the pump and its connecting piping), the process is adiabatic. The temperature of the water in the collection basin closely approaches the thermodynamic wet-bulb temperature of the entering air. But it cannot be brought to complete saturation.  Air washers are commonly available from 2000 to 250,000 cfm  (3500 to 400,000 m³/h) capacity.

            NO Input data.

----------------------------------------------------------------------------------------------------------------------

The water spray device. Cooled recirculated water

            A water spray device. (cooled recirculated water).

 Air washers and rigid-media direct evaporative coolers may be used to cool and dehumidify air. The heat and moisture are removed from the air causes the water temperature to rise. If the entering water temperature is below the entering air dew point, both the dry- and wet-bulb temperatures of the air is reduced, resulting in cooling and dehumidification. The air is typically saturated as it leaves. The vapor pressure difference between the entering air and the water cools the air. Moisture is transferred from the air to the water and  condensation occurs. The air leaving an evaporative dehumidifier is typically saturated, usually with less than 1°F ( 0.5°C ) difference between leaving dry- and wet-bulb temperatures. Final water conditions are typically 1 to 2°F ( 1°C ) below the leaving air temperature, depending on the saturation effectiveness of the device used.

            Optional Input:

Chilled water supply and return temperatures ( t1w and t2w ) for cooling recirculated water.

----------------------------------------------------------------------------------------------------------------------

The water spray device. (Heated recirculated water). 

 If heat is added to the water, the process state point of the mixture moves toward the temperature of the heated water. Elevating the water temperature makes it possible to raise the air temperature, both dry-bulb and wet-bulb, above the dry-bulb temperature of the entering air with the leaving air becoming fully saturated.

            Optional Input:

Hot water supply and return temperatures ( t1w and t2w ) for heating recirculated water.

----------------------------------------------------------------------------------------------------------------------

Steam Humidifier

 Humidification by addition of steam to air.

In isothermal humidification, water is carried until boiling to be dispersed in the air. Direct Steam Injection electric Humidifiers. Steam is water vapor under pressure and at high temperature, so the process of humidification can be simplified by adding steam directly into the air. This method is an isothermal process because the temperature of the air remains almost constant as the moisture is added. For this type of humidification system, the steam source is usually a central steam boiler at low pressure.

            NO Input data.

----------------------------------------------------------------------------------------------------------------------

Heat Recuperator

 The heat recovery device raises the enthalpy (temperature) of the air during cold weather (heating recuperator) by transferring energy between the ventilation air supply and exhaust airstreams.

Energy recovery devices is sensible heat devices (i.e., transferring sensible energy only) . In principle, there are two types of heat recuperating systems: Air-to-Air  and  Air-Liquid-Air.

For this calculation, the type of device makes no difference. The only thing you need is how much a device capable ( kW or Btu/h ) of  heat transmitting.  This is why it is necessary to calculate the appropriate type of device in advance.

            Required Input data:

Heat rate ( kW or Btu/h ).

----------------------------------------------------------------------------------------------------------------------

Cold Recuperator

 The heat recovery device lowers the enthalpy of the building supply air during warm weather (cooling recuperator)  by transferring energy between the ventilation air supply and exhaust airstreams.

Energy recovery devices may be sensible heat devices (i.e., transferring sensible energy only) or total heat devices (i.e., transferring both sensible energy and moisture). In principle, there are two types of heat recuperating systems: Air-to-Air  and  Air-Liquid-Air.

For this calculation, the type of device makes no difference. The only thing you need is how much a device capable ( kW or Btu/h ) of  heat transmitting. This is why it is necessary to calculate the appropriate type of device in advance.

            Required Input data:

Heat rate ( kW or Btu/h ).

----------------------------------------------------------------------------------------------------------------------

Desiccant Dehumidification

The desiccant takes out the moisture of the process airstream, heats the process airstream and places the moisture into a different airstream.

Desiccant-based systems are useful for reaching low dew points (below 43°F ( 6°C )) . A desiccant wheel is nice where conventional refrigeration no longer can work.

Cooling and desiccant dehumidification systems are most economical when used together, so the advantages of each compensate for the limitations of the other.

Theoretically as moisture is removed from the air, its enthalpy stays constant, so its sensible temperature rises. In fact, the enthalpy of the process air — air being dehumidified — actually increases slightly. This is because in many dehumidifiers, a small amount of residual heat from desiccant reactivation can be carried into the dry airstream. So actual results depend on the type and construction of dryer and calculation results are indicative. If you have dry airstream properties (after dryer), enter them as input data for calculation.