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Research of Joshua M. Rocklage


Figure 1: The CKV Group

For the past decade, the HVAC laboratory at the University of Minnesota - Twin Cities has been among the foremost research institutions in Commercial Kitchen Ventilation (CKV) related issues. This began with the ASHRAE research project, 745-RP [1], in 1998. The purpose of this work was to fully characterize the effluent emissions from various grease producing cooking processes. [2][3] Testing involved ten appliances, including gas and electric versions of griddles, open deep fat fryers, under-fired broilers, convection ovens, and ranges.

Figure 2: ASHRAE 745-RP Phase II Final Report

Figure 3: Average Total Grease Emissions per Appliance

In 2001, an ASHRAE sponsored research project, 1033-RP, was conducted to determine the effects of exhaust air velocity on grease deposition in kitchen exhaust ductwork. [4][5] This research resulted in the modification of the National Fire Protection Association (NFPA) Standard 96, the Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations, in 2001. It was determined that an average duct exhaust velocity of 500 fpm (depending on successful capture and containment) resulted in lower grease deposition rates than the (then) current rate of 1500 fpm due to turbulent deposition. This change is shown in Figure 4 below, Errata No. 96-01-01.

Figure 4: NFPA 96 Errata

The purpose of the most recent research has been to develop a standard method of test for commercial kitchen ventilation system filters. [6][7] The project consisted of determining the particle removal fractional efficiency of a set of filters using particles generated from the cooking of hamburgers, and then determining a suitable surrogate. Liquid oleic acid particles were settled on as the challenge aerosol. The test procedure was then finalized and fully validated, and has recently been adopted by ASTM as Standard F2519-05. The purpose of the Method of Test (MOT) is to provide ventilation system designers with the ability to select a filter system best suited to a particular application. [8] This standard can be found through ASTM at: ASTM Standard F2519-05.

Several grease filters were used for the development of the MOT. They are shown below in Figure 5 and Figure 6.

Figure 5: Test Filter

Figure 6: Test Filter

There are two important parameters related to the operation of CKV grease filters. They are the capture efficiency of the filter vs. particle diameter, and the pressure drop across the filter at airflow rates of interest. These parameters are shown graphically as an example in Figure 7 and Figure 8 below.

Figure 7: Particle Capture Efficiency vs. Particle Diameter

Figure 8: Pressure Drop vs. Airflow Rate


[1] Gerstler, W.D., T.H. Kuehn, D.Y.H. Pui, J.W. Ramsey, M.J. Rosen, R.R. Carlson, and S.D. Petersen. (1998) Identification and Characterization of Effluents from Various Cooking Appliances and Processes as Related to Optimum Design of Kitchen Ventilation Systems. ASHRAE 745-RP Final Report, University of Minnesota, Minneapolis.

[2] Gerstler, W.D., T.H. Kuehn, D.Y.H. Pui, J.W. Ramsey, (1999) Measurements of the Effluent from Hamburger Cooked on a Gas Under Fired Broiler. ASHRAE Transactions, Vol. 105, Part 2, pp.303-315.

[3] Gerstler, W.D., T.H. Kuehn, D.Y.H. Pui, J.W. Ramsey, (1999) Comparison of Emissions from Selected Commercial Kitchen Appliances and Food Products. ASHRAE Transactions, Vol. 105, Part 2, pp. 128-141.

[4] Kuehn, T.H., W.D. Gerstler, H.B. Ortiz, A. Sandquist, H.L. Tjandra, J.J. Vidhani, J.W. Ramsey, and D.Y.H. Pui. (2001) Effects of Air Velocity on Grease Deposition in Exhaust Ductwork. ASHRAE 1033-RP Final Report, Minneapolis: University of Minnesota.

[5] Gerstler, W.D., T.H. Kuehn, D.Y.H. Pui, J.W. Ramsey. (2002) The Effects of Exhaust Air Velocity on Grease Deposition in Kitchen Exhaust Ductwork. ASHRAE Transactions, Volume 108, Part 1, pp. 470-482.

[6] Kuehn, T. H., Olson, B. A., Ramsey, J. W., Friell, J. and Rocklage, J. M., (2004) Development of a Standard Method of Test for Commercial Kitchen Effluent Grease Removal Systems, Final Report, Department of Mechanical Engineering, University of Minnesota, Minneapolis.

[7] ASTM F2519-05, (2004) Standard Test Method for Grease Particle Capture Efficiency of Commercial Kitchen Filters and Extractors, ASTM International.

[8] Schrock, D., Kuehn, T., Breitenfeldt. A., Urness, R., Olson, B., (2006) A New Standard Method of Test for Determining the Grease Particulate Removal Efficiency of Filter Systems for Kitchen Ventilation, to be published, ASHRAE Transactions, Part 1.

ASHRAE 1375-RP Long Beach Presentation (New Window)


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Current Research of:

Past Research of:

Weihua Tang
Meng Zhang
Joshua Rocklage
Nicholas Stanley
Nikhil Ramesh


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