Portable Evaporative Cooler

Overview

A portable evaporative cooler, often called a swamp cooler, lowers air temperature by evaporating water rather than running a compressor. Warm dry air is pulled through a thick wet pad; as the water evaporates it absorbs heat from the air, and the air leaves several degrees cooler and more humid. Because there is no refrigerant loop or compressor, the unit is light, cheap to run, and easy to roll between rooms, at the cost of working well only in dry climates.

The machine is organized around airflow and water. The Blower Assembly pulls air through the Cooling Pad System, which the Water System keeps continuously wet. The Air Path directs the intake and the cooled output, the Cabinet & Chassis carries the whole assembly on casters, and a Control Board & Panel board manages speed, the pump, and the swing vanes.

How evaporative cooling works

The physics is the difference between dry-bulb and wet-bulb temperature. Hot dry air holds a large capacity to absorb water vapor. When that air passes over the wet Cooling Pad (Cellulose Media), some water evaporates, and the energy for that phase change comes from the air itself, so the air temperature drops. The dryer the incoming air, the larger the achievable drop. In humid air the gap between dry-bulb and wet-bulb is small, so the cooler does little and mostly just adds moisture. This is why the product is matched to arid regions and shoulder-season use.

Blower

The Blower Assembly moves the air. Unlike a bladed fan, an evaporative cooler uses a centrifugal Blower Wheel (Squirrel Cage), a forward-curved squirrel-cage rotor inside a Blower Scroll Housing scroll. The squirrel cage develops enough static pressure to pull air through the dense, water-laden pads, which a simple axial fan could not do. A multi-tap Blower Motor drives the wheel; its Stator Assembly, Rotor Assembly, and tapped Copper Winding sit in a Motor Housing and turn on two Ball Bearing supports. A Run Capacitor starts the motor and a Thermal Protector guards against overheating. The motor sits on a resilient Motor Mount so blower vibration does not transmit into the cabinet.

Cooling pad system

The Cooling Pad System is the heart of the cooler. Three rigid Cooling Pad (Cellulose Media) panels of corrugated cellulose, each about 100 mm thick, present a large wetted surface to the air. Water trickles down from a Water Distribution Tray across the top of each pad, fed by a Distribution Tube from the pump, and soaks the media evenly. Air drawn through the corrugations contacts the wet surface and picks up moisture. Each pad sits in a Pad Frame behind an outer Pad Screen that blocks debris and keeps the media in place. Cellulose pads outlast the older aspen-fiber type and resist the sagging that reduces coverage as the media wets and dries.

Water system

The Water System recirculates water so the pads never dry out. A Water Tank/Reservoir in the base holds about 35 litres. A submersible Recirculation Pump, a magnetic-drive unit with a Pump Impeller in a Pump Housing, lifts water up to the distribution tray; whatever the pads do not evaporate drains back to the tank. A Float Valve can top up the tank from a hose for unattended running, while a Water Level Sensor sensor warns when the reservoir is low so the pump does not run dry. A Drain Valve empties the tank for cleaning, and a Ice Tray lets the user drop in ice packs for a short extra boost on the hottest afternoons.

Air path and cabinet

The Air Path shapes the airflow. Side Inlet Louver panels admit room air to the pads, a Air Pre-Filter catches dust before it reaches the wet media, and motorized Outlet Vane louvers spread the cooled output. A small Vane Swing Motor oscillates the vanes so cooled air covers the room rather than blowing in one fixed direction.

The Cabinet & Chassis is a molded shell, a Front Housing Panel and Rear Housing Panel over the internals, riding on four Swivel Caster wheels for easy repositioning, with two of them locking. A top Carry Handle helps lift the unit when the tank is drained.

Control and power

The Control Board & Panel section runs the user interface from a Display Panel and an IR Remote handset. The Control Board carries an Microcontroller that sequences three Relay outputs for the blower speed, the pump, and the vane swing, and adds timer and sleep modes that ramp the fan down at night. Power enters through the Power & Wiring section: a Power Cord & Plug, a Strain Relief, and a Wire Bundle distributing mains to the motor, pump, and board.

Use and maintenance

Evaporative coolers need fresh air, so they run with a window cracked to vent the added humidity, unlike a closed-room air conditioner. Maintenance centers on the pads and water: scale and biofilm build up in hard water, so the tank should be drained and the pads rinsed or replaced each season. Running the blower alone for a few minutes after the pump shuts off dries the pads and discourages mold.