Control Principle of Rotary Heat Recovery Air Conditioning Unit

A rotary heat-recovery air-conditioning unit is a high-efficiency device that combines rotary heat-recovery technology with an air-conditioning system. Its control principle revolves around energy recovery, air treatment, and operational optimization. The following is a brief explanation of its control principle:

1. Basic Principle of Rotary Heat Recovery

The core component is a slowly rotating honeycomb wheel, usually made of aluminum alloy or corrosion-resistant materials, and available in sensible-heat and total-heat types:

• Sensible-Heat Exchangefresh air and exhaust air pass countercurrently through the two semicircular zones of the wheel; in winter the exhaust heat is transferred to the cold fresh air, and vice versa in summer.
• Total-Heat Exchangethe total-heat wheel uses hygroscopic material to transfer both humidity and temperature simultaneously. The wheel speed is typically 10–20 rpm, driven by a motor and adjustable according to heat-recovery efficiency requirements.

2. Control Principle and System Composition

The control system achieves automatic operation through sensors, controllers, and actuators, ensuring energy savings and indoor comfort. Its main components and logic are:

• Sensorsmonitor the temperature, humidity, and airflow of fresh and exhaust air, as well as indoor and outdoor environmental parameters.
• Controller(such as PLC or DDC): based on sensor data, uses algorithms to adjust the wheel speed, fan airflow, and cooling/heating capacity.
• Actuators：
  • Wheel drive motorcontrols the wheel speed to optimize heat-exchange efficiency.
  • Variable-frequency fanadjusts fresh-air and exhaust-air volumes to balance system pressure and save energy.
  • Valves and compressorthe direct-expansion air-conditioning section regulates cooling/heating by controlling refrigerant flow and compressor operation.
• Control Logic：
  • Heat-recovery optimizationadjust the wheel speed according to temperature and humidity differences to maximize energy recovery.
  • Indoor comfortmonitor indoor temperature and humidity, and adjust fresh-air volume and air-conditioning output to maintain set parameters.
  • Energy-saving modeunder low load or small temperature differences, reduce the wheel speed or fan power to lower energy consumption.

3. Typical Control Process

1. Data acquisitionsensors collect fresh-air, exhaust-air, indoor/outdoor temperature and humidity, and CO2 concentration in real time.
2. Data analysisthe controller compares the set targets (e.g., indoor temperature 26°C, humidity 50%) with real-time data to calculate the heat-recovery amount and air-conditioning output.
3. Execution and adjustment：
   • Adjust the wheel speed to optimize heat-recovery efficiency (e.g., increase the speed when the winter temperature difference is large).
   • Control the fan airflow to meet ventilation needs and avoid excessive air exchange.
   • Coordinate the direct-expansion air conditioner for cooling/heating to supplement the insufficient cooling/heating from heat recovery.
4. Feedback optimizationcontinuously monitor operating results and dynamically adjust component states.