Using LabVIEW and NI USB DAQ to Build an Automatic Heat Ventilation

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"We built and tested an effective, real-time automatic heat ventilation system based on natural environmental cooling concepts using a USB-6008 and LabVIEW."

- Rodney Tan , University College Sedaya International

The Challenge:
Adapting the temperature of a fan-based heat ventilation system in reaction to environmental temperature changes to better manage energy efficiency.

The Solution:
Developing an automatic heat ventilation system using an exterior environment temperature sensor, an interior system temperature sensor, an NI USB-6008 DAQ device for temperature acquisition, and NI LabVIEW software as the processing platform for matching and maintaining the interior and exterior temperatures using a ventilation fan.

Author(s):
Rodney Tan - University College Sedaya International
T.K Low - University College Sedaya International
A. C. Tan - University College Sedaya International

Electrical and mechanical systems such as a computers, power supply units, amplifiers, machinery rooms, or vehicle interiors generate heat during operation. Most electrical and mechanical systems are installed and assembled inside some sort of casing, housing, or maybe even an entire room, to protect them from being touched or exposed to unnecessary contact that may injure an operator or cause a system malfunction. The casing serves as a protective housing for the system but it also accumulates and traps heat within the system if it’s not properly ventilated.

A heating, ventilation, and air conditioning (HVAC) system is a common solution for room-based systems. HVAC systems provide temperature control regardless of surroundings or exterior environment temperature. However, HVAC systems are costly because of the additional power consumed by the air conditioning unit for the heat exchange process, so they are not energy efficient. Fan-based ventilation systems with preset temperature setpoints are a common solution to smaller casing or housing-based electrical systems. The preset temperature setpoint is usually fixed and does not change even if the system is placed in a cooler or hotter environment. The proposed fan-based heat ventilation system uses natural environmental cooling concepts where the cooling factor or the interior temperature setpoint is determined by the surrounding external environmental temperature. This allows the temperature setpoint to change and adapt to the temperature of the surrounding environment for better thermal management in terms of cooling efficiency.

System Overview

Our automatic heat ventilation system uses two National Semiconductor LM35 temperature sensors, one for interior temperature sensing and the other for exterior environmental temperature sensing. We use the analog inputs on the USB-6008 to acquire both temperatures at the same time. The USB-6008 device uses one digital output for fan activation. We built a small system model to simulate a system that generates internal heat within the system. A 100 W lightbulb is the internal heat source to simulate convection heat generated by the system. We placed two ventilation fans on both ends of the model to remove heat from the system. Figure 1 shows the heat ventilation system overview.

The user interface (UI) has two thermometer bars, two temperature numerical displays, a temperature chart, and a fan activation indicator. The UI does not provide system interaction because it’s not necessary for an operator to determine the temperature setpoint for fan activation. It is mainly used for monitoring. Figure 2 shows the automatic heat ventilation system LabVIEW UI.

When the user runs the LabVIEW program, the UI shows both the interior and exterior temperature in the thermometer bar in the numerical display as well as the temperature chart. In normal conditions the interior temperature is higher than the exterior temperature. In this condition the fan indicator activates to show that the ventilation fan is running. The system tries to match the heated interior temperature to the cooler exterior temperature by releasing heat from the system. The temperature chart on the UI shows the temperature dropping gradually toward the exterior temperature setpoint.

Results and Discussion

We performed a few experiments to test the automatic heat ventilation system. In the first experiment, we heated the system interior to a peak temperature of 50 °C without ventilation in an exterior temperature of 31 °C. The fan ventilation was then initiated. From the LabVIEW UI we observed that the interior temperature dropped gradually down to 33 °C in six minutes and the temperature was maintained even when the heat source was still on. Once the heat source was turned off, the interior temperature dropped from 33 °C to 31 °C in two minutes and the fans automatically deactivated since the interior temperature already matched the exterior temperature.

The next experiment involved turning on the internal heat source again. Once the interior temperature rose higher than 31 °C, the fans were activated to prevent the interior temperature from further rising. The interior temperature was maintained at 33 °C after two minutes with the heat ventilation system maintaining the minimum possible interior temperature. The temperature setpoint was determined by the exterior temperature and it adapted according to the environmental temperature changes.

Conclusion

We built and tested an effective, real-time automatic heat ventilation system based on natural environmental cooling concepts using a USB-6008 and LabVIEW. The system works effectively in real time and the natural environmental cooling concept ensures the heat ventilation system maintains the minimum possible interior temperature with the setpoint temperature determined by the exterior environment temperature. The ventilation is deactivated when the interior temperature matches the exterior temperature, thus preventing unnecessary ventilation and saving energy.

Author Information:
Rodney Tan
University College Sedaya International
No. 1 Jalan Menara Gading, UCSI Heights
Kuala Lumpur 56000
Malaysia
Fax: +60391023606
rodneyt@ucsi.edu.my

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