Dehumidification Calculator

Psychrometric Water Generation Calculator

Atmospheric Water Generator / Dehumidifier Sizing – Based on Full Psychrometric & Enthalpy Model

1. Select Primary Input

Water (L/day)

Power (W)

Cooling (W)

Cooling (Btu/h)

Enter Water Production (L/day):

2. System & Psychrometric Assumptions

Psychrometric Conditions

Ambient Temp (°C)

Ambient RH (%)

Evap. Coil Temp (°C)

Pressure (Pa)

Common System Assumptions

Compressor COP

Latent Heat h_fg (J/kg)

Evaporator U (W/m²·K)

Condenser U (W/m²·K)

Condenser ΔT (K)

3. Formulas Used

All enthalpies in kJ/kg (converted to J/kg inside the code). Standard ASHRAE moist air relations.

Psychrometrics

• Humidity ratio: $$ \omega = 0.622 \cdot \frac{P_w}{P_{atm} - P_w} \quad [\text{kg water/kg dry air}] $$
• Water vapour partial pressure: $$ P_w = RH \cdot P_{ws}(T) \quad [\text{Pa}] $$
• Saturation pressure (Magnus-type): $$ P_{ws}(T) \approx 610.78 \, e^{\left(\frac{17.27T}{T+237.3}\right)} \quad [\text{Pa}] $$
• Humidity ratio difference: $$ \Delta \omega = \omega_{in} - \omega_{coil} \quad [\text{kg water/kg dry air}] $$

Enthalpy (ASHRAE)

• Moist air enthalpy: $$ h = 1.006T + \omega(2501 + 1.86T) \quad [\text{kJ/kg dry air}] $$
• Enthalpy difference per kg dry air: $$ \Delta h = h_{in} - h_{coil} \quad [\text{kJ/kg}] $$

Mass Flow & Water

• From water to mass flow: $$ \dot{m}_w = \frac{W_{\text{day}}}{86400} \quad [\text{kg/s}] $$
• Dry air mass flow: $$ \dot{m}_{air} = \frac{\dot{m}_w}{\Delta \omega} \quad [\text{kg/s}] $$
• Or from cooling: $$ \dot{m}_{air} = \frac{\dot{Q}_{total}}{\Delta h} \quad [\text{kg/s}] $$
• Water from air: $$ \dot{m}_w = \dot{m}_{air} \Delta \omega \quad [\text{kg/s}] $$

Heat Loads

• Total cooling: $$ \dot{Q}_{total} = \dot{m}_{air} \Delta h \quad [\text{W}] $$
• Latent cooling: $$ \dot{Q}_{latent} = \dot{m}_{air} \Delta\omega \, h_{fg} \quad [\text{W}] $$
• Sensible cooling: $$ \dot{Q}_{sensible} = \dot{Q}_{total} - \dot{Q}_{latent} \quad [\text{W}] $$
• Compressor power: $$ P_{in} = \frac{\dot{Q}_{total}}{COP} \quad [\text{W}] $$

Coil Areas

• Evaporator ΔT: $$ \Delta T_{evap} = T_{in} - T_{coil} \quad [\text{K}] $$
• Evaporator area: $$ A_{evap} = \frac{\dot{Q}_{total}}{U_{evap} \Delta T_{evap}} \quad [\text{m}^2] $$
• Condenser heat rejection: $$ \dot{Q}_{cond} = \dot{Q}_{total} + P_{in} \quad [\text{W}] $$
• Condenser area: $$ A_{cond} = \frac{\dot{Q}_{cond}}{U_{cond} \Delta T_{cond}} \quad [\text{m}^2] $$

Calculation Results

Please enter valid numbers for all fields and ensure condensation is possible (Δω > 0, Δh > 0).

Key Metrics

Water Production: -- L/day

Compressor Input: -- W

Total Cooling Load: -- W

Cooling Breakdown

Total Cooling (Btu/h): -- Btu/h

Latent Cooling: -- W

Sensible Cooling: -- W

Condenser Heat Rejection: -- W

Psychrometric Details

Humidity Ratio Inlet (ω_in): -- kg/kg

Humidity Ratio Coil (ω_coil): -- kg/kg

Δω (Moisture Difference): -- kg/kg

Enthalpy Inlet (h_in): -- kJ/kg

Enthalpy Coil (h_coil): -- kJ/kg

Δh (h_in - h_coil): -- kJ/kg

Mass Flow & Airflow

Water Mass Flow: -- kg/s

Dry Air Flow: -- kg/s

Air Flow (m³/s): -- m³/s

Air Flow (m³/h): -- m³/h

Coil Temperatures & Areas

Evaporator ΔT (T_in - T_coil): -- K

Required Evaporator Area: -- m²

Required Condenser Area: -- m²