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Title: Laser sheet light flow visualization for evaluating room air flowsfrom Registers

Abstract

Forced air heating and cooling systems and whole house ventilation systems deliver air to individual rooms in a house via supply registers located on walls ceilings or floors; and occasionally less straightforward locations like toe-kicks below cabinets. Ideally, the air velocity out of the registers combined with the turbulence of the flow, vectoring of air by register vanes and geometry of register placement combine to mix the supply air within the room. A particular issue that has been raised recently is the performance of multiple capacity and air flow HVAC systems. These systems vary the air flow rate through the distribution system depending on the system load, or if operating in a ventilation rather than a space conditioning mode. These systems have been developed to maximize equipment efficiency, however, the high efficiency ratings do not include any room mixing effects. At lower air flow rates, there is the possibility that room air will be poorly mixed, leading to thermal stratification and reduced comfort for occupants. This can lead to increased energy use as the occupants adjust the thermostat settings to compensate and parts of the conditioned space have higher envelope temperature differences than for the well mixed case. In addition,more » lack of comfort can be a barrier to market acceptance of these higher efficiency systems To investigate the effect on room mixing of reduced air flow rates requires the measurement of mixing of supply air with room air throughout the space to be conditioned. This is a particularly difficult exercise if we want to determine the transient performance of the space conditioning system. Full scale experiments can be done in special test chambers, but the spatial resolution required to fully examine the mixing problem is usually limited by the sheer number of thermal sensors required. Current full-scale laboratory testing is therefore severely limited in its resolution. As an alternative, we used a water-filled scale model of a room in which whole-field supply air mixing maps of two vertical planes were measured using a Planar Laser-Induced Fluorescence (PLIF) measurement technique. Water marked with fluorescent dye was used to simulate the supply airflow; and the resulting concentrations within the water filled model show how the supply air mixes with the room air and are an analog for temperature (for thermal loads) or fresh air (for ventilation). In addition to performing experiments over a range of flow rates, we also changed register locations and examined the effects for both heating and cooling operation by changing the water density (simulating air density changes due to temperature changes) using dissolved salt.« less

Authors:
; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE. Office of Energy Efficiency and RenewableEnergy
OSTI Identifier:
924836
Report Number(s):
LBNL-56483
R&D Project: 00000; TRN: US200809%%697
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
32; AIR FLOW; COOLING SYSTEMS; EFFICIENCY; FLOW RATE; FLOW VISUALIZATION; FLUORESCENCE; HVAC SYSTEMS; LASERS; SCALE MODELS; SPATIAL RESOLUTION; THERMOSTATS; VENTILATION; VENTILATION SYSTEMS; WATER

Citation Formats

Walker, Iain S., Claret, Valerie, and Smith, Brian. Laser sheet light flow visualization for evaluating room air flowsfrom Registers. United States: N. p., 2006. Web. doi:10.2172/924836.
Walker, Iain S., Claret, Valerie, & Smith, Brian. Laser sheet light flow visualization for evaluating room air flowsfrom Registers. United States. doi:10.2172/924836.
Walker, Iain S., Claret, Valerie, and Smith, Brian. Sat . "Laser sheet light flow visualization for evaluating room air flowsfrom Registers". United States. doi:10.2172/924836. https://www.osti.gov/servlets/purl/924836.
@article{osti_924836,
title = {Laser sheet light flow visualization for evaluating room air flowsfrom Registers},
author = {Walker, Iain S. and Claret, Valerie and Smith, Brian},
abstractNote = {Forced air heating and cooling systems and whole house ventilation systems deliver air to individual rooms in a house via supply registers located on walls ceilings or floors; and occasionally less straightforward locations like toe-kicks below cabinets. Ideally, the air velocity out of the registers combined with the turbulence of the flow, vectoring of air by register vanes and geometry of register placement combine to mix the supply air within the room. A particular issue that has been raised recently is the performance of multiple capacity and air flow HVAC systems. These systems vary the air flow rate through the distribution system depending on the system load, or if operating in a ventilation rather than a space conditioning mode. These systems have been developed to maximize equipment efficiency, however, the high efficiency ratings do not include any room mixing effects. At lower air flow rates, there is the possibility that room air will be poorly mixed, leading to thermal stratification and reduced comfort for occupants. This can lead to increased energy use as the occupants adjust the thermostat settings to compensate and parts of the conditioned space have higher envelope temperature differences than for the well mixed case. In addition, lack of comfort can be a barrier to market acceptance of these higher efficiency systems To investigate the effect on room mixing of reduced air flow rates requires the measurement of mixing of supply air with room air throughout the space to be conditioned. This is a particularly difficult exercise if we want to determine the transient performance of the space conditioning system. Full scale experiments can be done in special test chambers, but the spatial resolution required to fully examine the mixing problem is usually limited by the sheer number of thermal sensors required. Current full-scale laboratory testing is therefore severely limited in its resolution. As an alternative, we used a water-filled scale model of a room in which whole-field supply air mixing maps of two vertical planes were measured using a Planar Laser-Induced Fluorescence (PLIF) measurement technique. Water marked with fluorescent dye was used to simulate the supply airflow; and the resulting concentrations within the water filled model show how the supply air mixes with the room air and are an analog for temperature (for thermal loads) or fresh air (for ventilation). In addition to performing experiments over a range of flow rates, we also changed register locations and examined the effects for both heating and cooling operation by changing the water density (simulating air density changes due to temperature changes) using dissolved salt.},
doi = {10.2172/924836},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}

Technical Report:

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  • Field testing was performed in a retrofit unoccupied test house in Fresno, California. Three air-based heating, ventilation, and air conditioning (HVAC) distribution systems - a typical airflow ducted system to the bedrooms, a low airflow ducted system to the bedrooms, and a system with no ductwork to the bedrooms - were evaluated during heating, cooling, and midseason conditions. The relative ability of each of the three systems was assessed with respect to relevant Air Conditioning Contractors of America (ACCA) and ASHRAE standards for house temperature uniformity and stability, respectively. Computational fluid dynamics (CFD) modeling also was performed and refined basedmore » on comparison to field test results to determine the air flow rate into the bedrooms of over-door and bottom-of-door air transfer grilles.« less
  • A synchronous, strobed laser light sheet has been developed for use in flow visualization of a helicopter rotor model. The light sheet strobe circuit included selectable blade position, strobe duration, and multiple pulses per revolution for rotors having 2 to 9 blades. The flow was seeded with propylene glycol. Between runs, a calibration grid board was placed in the plane of the laser sheet and recorded with the video camera at the position used to record the flow field. A slip-sync mode permitted slow motion visualization of the flow field over complete rotations of the rotor. The system was usedmore » to make two-dimensional flow field cuts of a four-bladed rotor operating at advance ratio of 0.37 at wind tunnel speeds up to 79.25 meters per second (260 feet per second).« less
  • This report presents test results of flow visualization in a chemical laser cavity. Holograms were recorded of supersonic flow from a two-dimensional slit nozzle during test runs of HF or DF lasing. Laser cavity pressure was nominally 2 torr. Holographic reconstruction gave schlierens and shadowgraphs which were used to qualitatively define Mach numbers and nozzle exit plane boundary layers.
  • A facility to characterize the airflow at the exit of HVAC registers was designed and fabricated. The objective of this work is to obtain velocity and turbulence data at the exit of registers, which can then be used as an input boundary condition in a modern Computational Fluid Dynamics (CFD) code to predict the velocity and temperature distribution in an enclosure, and also the register performance parameters such as throw. During the course of this work, two commonly used registers were tested. Both registers were 8 inch x 4 inch sidewall registers. Laser Doppler Velocimetry was used to measure themore » axial and vertical components of the velocity vector at various locations across the face of the registers. For the two cases of registers studied here, the results suggest that the velocity field at the very exit of each of these registers scales with the flow rate through the registers. This means that, in the mode of operation in which the supply fan (of an HVAC system) has a ''High'' and ''Low'' setting, similar velocity scaling would result for the type of registers tested here.« less