Masters Theses


"Air mixing is a problem that has attracted engineers from many fields. HV AC is one of those fields in which air mixing damper systems with economizer control has been used for providing energy conservation and to provide ventilation air to building occupants. It has been assumed that if parallel blade dampers are used and if the blades are aligned to force mixing of outside air and return air, the air will mix sufficiently to prevent thermal stratification thereby avoiding all further problems caused by it. There is no definitive data available on the mixing performance of dampers that can help the engineers in designing the mixing boxes. Also it is believed that if the two air streams are mixed sufficiently to give uniform temperatures then the gaseous components in the streams also mix uniformly.

Mixing of two air streams with different temperatures and different gaseous compositions was studied. The two air streams represent the return air and outside air in air handling unit (AHU). Mixing of these two streams is done with the help of a pair of parallel blade dampers, which direct the two streams towards each other. Two different damper configurations, which are commonly used in the HV AC industry are identified and were tested. The main aim of this thesis is to identify the configurations that provide adequate mixing and to produce guidelines for the design of mixed air damper configurations. The study also investigates the effect of damper orientation, relative velocities of two air streams through the dampers, and blade sizes on the mixed air temperatures and concentrations measured just off the mixing plenum.

The results of the testing quantify both thermal and gaseous mixing achieved and also identifies the best and the worst cases in the configurations tested. The study reveals important aspect about thermal and gaseous mixing along with the effects of parameters like damper orientation, relative air velocities, and blade size on it. Lastly the results also touch on the issue of relation between both thermal and gaseous mixing characteristics of the mixed air dampers"--Abstract, page iii.


Sauer, Harry J., Jr., 1935-2008

Committee Member(s)

Finaish, Fathi
Kluczny, Raymond Michael


Mechanical and Aerospace Engineering

Degree Name

M.S. in Mechanical Engineering


American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE)


University of Missouri--Rolla

Publication Date

Spring 2001


xii, 109 pages

Note about bibliography

Includes bibliographical references (pages 107-108).


© 2001 Milind Sudhakar Mainkar, All rights reserved.

Document Type

Thesis - Restricted Access

File Type




Subject Headings

Air flow
Air conditioning
Heating and ventilation industry

Thesis Number

T 7912

Print OCLC #


Electronic OCLC #


Link to Catalog Record

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