Calculation Formulas

Simplified selection of dehumidifiers

For approximate evaluation of required dehumidification mode and preliminary selection one can use empirical formulas taking into consideration two main requirements:

1. Dehumidification is performed in a closed room.

2. Room temperature corresponds to working temperatures range for the certain dehumidifier.

APPROXIMATE CALCULATION OF REQUIRED DEHUMIDIFICATION MODE

Designations:

Q – required moisture release rate, l/h

V – room volume, m3

Vw – volume of dehumidified wood, m3

Рw – density of dehumidified wood, kg/m3

S – pool surface area, m2


Detailed description of dehumidification systems engineering is shown in “Dehumidification systems design manual” Dantherm - 1998.

Sphere of application

Required moisture release rate, l/h

Conditions

Dry storage (warehouses)

Q = Vx 1.2 х 10-3

Ventilation rate 0.3 Dehumidification rate 2.5 g/m3 h Air temperature 20 °С

Dehumidification in living and administrative premises

Q = V х 1.5 х 10 -3

Ventilation rate 0.5 Dehumidification rate 2.5 g/m3 h Air temperature 20 °С

Dehumidification of buildings

Q = V х 2.0 х 10-3

Ventilation rate 0.3 Dehumidification rate (with consideration of humidity evaporation from soaked materials) 3.2 g/m3 h Air temperature 20 °С Dehumidification period – 8 days.

Dehumidification of wood

Q = Vw Х Рw X 0,4 Х 10 -3

Airtight drying camera. Air temperature 25-30 °С Relative humidity 30-40 % Dehumidification rate – 1% of wood moisture load in 24 hours.

Swimming-pools dehumidification

Private pools up to 50 m2 ( with protective covering, at partial load): Q = S х 0,public swimming pools over 50 m2 (without protective covering, at normal load): Q = S х 0.2

Affluence of ambient air - (10 х S) m3/h Air temperature - (t water + 2) °С relative air humidity - 60 %


FORMULA OF STANDARD VDI 2089

Evaporation rate is calculated as follows:

W = е х S х (Рrich - Рset) g/h;


Whereas:

S – swimming pool area, m2;

Рrich – pressure of water vapors in rich air at water temperature in the pool, mbar;

Рset - vapour fractional pressure at set air temperature and humidity, mbar;

е - empirical coefficient, g/(m2 х h х mbar):

0.5 – pool covered area,

5 – pool motionless area,

15 – small private swimming pools with limited number of swimmers,

20 - public swimming pools with usual number of swimmers,

28 – swimming pools for recreation and entertainment,

35 – swimming pools with water slides and significant wave formation.

Example. Private swimming pool.

Pool surface 20 х 5 m S= 100 m2

Water temperature 28 °С (100% rel. hum.) Rich= 37.78 mbar

Air temperature 30 °С (60 % rel. hum.) Рset= 25.45 mbar

Evaporation rate

W = 13 х 100 х (37.78-25.45)= 16029 g/h = 16 l/h


BYAZIN-KRUMME FORMULA


For the period when there are swimmers in the pool:

Wop = (0.118 + 0.01995 х а х (Рrich - Рset)/1,333) xSl/h,

For the period when there are no swimmers in the pool (water surface is blinded or filled with floating balls/balsa):

Wcl = (- 0.059 + 0.0105 (Рrich - Рset)/1,333) S l/h,

Whereas:

Rich – pressure of water vapors in rich air at water temperature in the pool, mbar;

Рset - vapour pressure of rich air at set air temperature and humidity, mbar;

а – pool attendance rate:

1,5 – for entertainment pools with active wave formation

0,5 – for large public swimming pools

0,4 – for hotel swimming pools

0.3 – for small private swimming pools