Visualization of diffuser outlet flow using liquid crystal sheets

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · ASHRAE Journal

OSTI ID:109829

Kirkpatrick, A T ^[1]

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1. Colorado State Univ., Fort Collins, CO (United States)

This article describes a new imaging technique to determine air temperatures and flow fields from HVAC diffusers. The technique uses liquid crystal sheets to record the airflow and temperatures in color. The air temperature field is an important contributor to the thermal comfort in a room and is used to evaluate diffuser performance. Visualization of the temperature field allows one to see directly the flow field and how it is interacting with the room air. a particular application is to cold-air distribution systems that supply cooling and ventilation air to rooms at temperatures lower than in conventional systems. In these systems the cold-air supply is as low as 39 F (4 C), instead of the conventional value of 55 F (13 C). This new technique uses a temperature-sensitive liquid crystal sheet to create a visual measuring tool. The liquid crystals are layered on a plane sheet and produce two-dimensional color images of the air temperature field. Since air is invisible, some type of indicator placed in the air stream is required to determine the air temperature. At present, instruments such as thermocouples and thermistors determine the air temperature in rooms and measure the value at a single point. Information about the temperature and flow field in a room is obtained by moving the device, or using multiple sensors. This is a time-consuming process, and only yields information at the points of measurement. However, the temperature field is usually unsteady, due to variable air currents and cooling loads, so a movable device is not entirely suitable, and multiple instruments require multiple data acquisition channels. It would be more informative to visualize the entire airflow from the diffuser at any instant. This article deals with a temperature characterization method.

• OSTI ID: 109829
• Journal Information: ASHRAE Journal, Journal Name: ASHRAE Journal Journal Issue: 8 Vol. 38; ISSN ASHRAA; ISSN 0001-2491
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
AIR FLOW
DIFFUSERS
FLOW RATE
FLOW VISUALIZATION
SPACE HVAC SYSTEMS
VENTILATION SYSTEMS