Identity

A direct evaporative heat-exchange medium installed in negative-pressure ventilation systems designed to convert sensible heat into latent heat of vaporization.

Overview

Evaporative Cooling Pads are a critical climate control component utilized within tunnel-ventilated houses to combat heat stress. Constructed primarily from specialized cellulose media, these pads successfully drop the intake air dry-bulb temperature, proving highly effective for dry heat management in low-humidity environments.

Structured Facts

Classification

Heating & Cooling Infrastructure / Cellulose Cooling Media.

Purpose

To lower incoming dry-bulb air temperatures through the evaporation of water, actively converting sensible heat from the incoming airstream into latent heat of vaporization without changing total enthalpy.

Design & Construction

Manufactured from cross-corrugated cellulose paper sheets treated with anti-rot and wetting agents. The corrugations are bonded at alternating angles, commonly featuring a 45°-45° or 30°-30° geometry to maximize the wet surface boundary area relative to the physical volume. Alternative materials tested include wood shavings, coir fiber, charcoal, luffa sponge, and sackcloth.

Environmental Controls

• Temperature: Reduces the dry-bulb temperature of the air.
• Humidity: Increases absolute and relative humidity.
• Ventilation: Must maintain specific air velocity targets to prevent water droplet carryover.
• Air Speed: Face velocity is strictly regulated based on pad thickness.

Capacity & Layout

Installed at the intake end of negative-pressure semi-EC or tunnel ventilated houses. Must maintain a minimum vertical height of 5.0 feet to ensure sufficient intake surface area.

Equipment Integration

Integrates with Tunnel Ventilated Houses, Smart Controllers, and Exhaust Fans.

Advantages

Highly effective in low-humidity dry heat environments. Cellulose pads consistently achieve high saturation efficiencies between 70% and 85%.

Limitations

If operated at incorrect velocities, water droplets carry over into the house. Mineral scaling blocks airflow if not treated. Effectiveness relies entirely on the house structural airtightness; leaks bypass the pads, destroying the pressure differential and causing uneven cooling.

Maintenance

Cellulosic pads must be descaled annually to remove mineral buildup that restricts airflow. Water filters must be cleaned weekly, and the upper water distribution pipe must be flushed regularly to prevent dry spots across the pad.

Quantitative Data

• Ventilation Rate: Static pressure drop of 17 to 77 Pa (0.07 to 0.31 inches of water column).
• Air Speed: Face velocity for 100 mm pads is 1.27 m/s; for 150 mm pads is 1.78 m/s.
• Dimensions: Pad thicknesses produced at 50 mm, 100 mm, and 150 mm (6-inch is industrial standard). Vertical height minimum 5.0 feet.

Relationships

• Equipment: Tunnel Ventilated House, Semi-EC House.
• Environmental Parameters: Dry-bulb Temp, Wet-bulb Temp, Latent heat of vaporization, Saturation Efficiency (η).
• Diseases: Heat Stress.
• Calculators: Saturation Efficiency formula η = ((T_db - T_exit) / (T_db - T_wb)) * 100%. Water flow rate: 1.0 L/s per square meter of horizontal top area. Vertical: 100 mm pad requires 5.0 L/min per linear meter; 150 mm pad requires 7.5 to 11.4 L/min per linear meter.