1、126 2009 ASHRAEThis paper is based on findings resulting from ASHRAE Research Project RP-1375.ABSTRACTThe main objective of this study was to characterize the grease emissions from seven common commercial kitchen cooking appliances and associated food products: 1) gas-fired conveyor broiler (hamburg
2、er), 2) gas/electric clamshell grid-dle (hamburger), 3) gas-fired conveyor pizza oven (thin crust pepperoni pizzas), 4) gas over-fired broiler (beef steak), 5) electric steamer (chicken breasts), 6) solid fuel broiler fueled by mesquite charcoal (hamburger), and 7) a gas-fired Chinese wok cooking di
3、ced chicken breasts in peanut oil. Emission measurements were made in the center of the plume above each appliance at the lower entrance to an eight foot canopy exhaust hood and in the center of the horizontal exhaust duct approx-imately 6 feet (2 m) downstream from the hood collar. No filters were
4、used in the hood for these measurements. Particulate data were obtained with 8-stage Personal Cascade Impactors for classification of particles between 0.5 and 15 m and Scanning Mobility Particle Sizers for classification of particles from 20 nm to 0.8 m. Most of the appliances generated relatively
5、large amounts of mass associated with particles larger than 10 m in diameter. However, most of these large particles were not observed in the exhaust duct indicating a loss mechanism such as impaction or settling between the bottom of the hood and the centerline of the exhaust duct. All appliances g
6、enerated a well defined aerosol mode with a maximum number concentration between 36 nm and 173 nm. The particle size distribution asso-ciated with these small particles did not change appreciably between the plume and the exhaust duct sampling locations indicating that this aerosol mode had already
7、reached equi-librium by the time it entered the exhaust hood. These fine aero-sol particles are not captured efficiently by conventional commercial kitchen grease filters that rely on impaction as the main particle removal mechanism.INTRODUCTIONEmissions from cooking processes includes effluent in b
8、oth particulate and vapor phases. Components of the effluent include water vapor, organic vapors, and particles that can include a variety of hydrocarbons, water, and solids such as elemental carbon. Some constituents may change phase as their concentration and temperature change throughout the emis
9、sion process. What may begin as a vapor may form particles as the effluent stream cools. For this reason, the U.S. EPA defines condensable particulate matter as any volatile material that may reside in particulate phase in the ambient environment. The objective of this paper is to report the results
10、 of a recent study supported by ASHRAE research, 1375-RP, where the effluent streams from seven commercial cooking appliances and food products were characterized both in the plume as the effluent entered an eight foot canopy exhaust hood, and in the exhaust duct downstream from the hood with no gre
11、ase filters present A prior paper reported the results of the total mass of effluent that was measured (Kuehn et al.2009) including total particulate mass and total condensable vapor mass. This paper focuses on the size distribution and concen-tration of the particles that were measured. The applian
12、ces were selected to extend the types studied previously (Kuehn et al., 1999). The food selected for each was intended to be representative for that appliance with a fairly high fat content to provide relatively high concentration of grease aerosol emissions. The appliances selected for study and th
13、e corresponding food product specifications are listed in Grease Particle Emission Characterization from Seven Commercial Kitchen Cooking Appliances and Representative Food ProductsThomas H. Kuehn, PhD, PE Bernard A. Olson, PhDFellow ASHRAEJames W. Ramsey, PhD Joshua M. RocklageMember ASHRAET.H. Kue
14、hn is professor and director of the Environmental Division, B.A. Olson is a research associate, J.W. Ramsey is a professor and asso-ciate department head, and J.M. Rocklage is a research assistant, Department of Mechanical Engineering, University of Minnesota, Minne-apolis, MN.LO-09-010 (RP-1375) 20
15、09, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE
16、s prior written permission.ASHRAE Transactions 127Table 1. Measurements were obtained in the plume above each appliance as in the earlier study using a personal cascade impactor that determined particle sizes from 0.5 to 15 microns. A second impactor sampled effluent from the unfiltered exhaust stre
17、am to determine the natural losses that occur between the two sampling points and to better characterize the effluent that may enter the ambient air. The exhaust duct was not sampled for most of the appliances in the previous study.One of the observations from the earlier study was that a significan
18、t fraction of the particulate mass emissions can occur in the submicron size range. This was especially true for broilers. In the previous study, these small particles were captured primarily by the after-filter in the personal cascade impactor and thus their size distribution was not determined. Ae
19、rosol measurement instrumentation has evolved since the earlier study and now several instruments are available to measure particles down to a few nanometers in size. A driving factor in the characterization of ultrafine particle emissions is their impact on human health (Oberdorster et al, 2005). B
20、ecause of the advancements in instrumentation capability and the perception that human health issues are associated with ultrafine particles, two Scanning Mobility Particle Sizers (SMPS) were added to the instrumentation package that cover the range from 20 nm to 0.8 m. Thus particles from 20 nm to
21、15 m in diameter are captured and quantified in both the effluent plume and in the exhaust duct.The following sections describe the test facility, the instrumentation used, the sampling and data reduction proto-cols, and the results. Recommendations are given on the effects of the effluents on indoo
22、r and outdoor environments and the need for improved commercial kitchen grease capture filters and extractors. TEST FACILITYThe test kitchen is located within the Mechanical Engi-neering Building at the University of Minnesota and was constructed and used in the previous ASHRAE 745-RP study. A detai
23、led description of the construction and operation is provided in Kuehn et al. (2009). Schematics of the test facility with the conveyor broiler installed are shown in Figure 1. Each appliance was centered under the exhaust hood from end to end as much as possible and recessed from the front of the h
24、ood by at least 6 in. (152 mm) to promote capture and containment of the effluent plume. The sample point in the plume was located near the point of highest temperature just below the hood opening. This was often determined both by measuring the plume temperature with a thermocouple and by visual ob
25、servation of the plume. For the appliances with well defined plumes, this was straightforward. For some appli-ances, such as the clamshell griddle where both sides operated separately, the plume shifted position over a cooking cycle and compromise locations were made to obtain repeatable effluent sa
26、mples. The sample location in the exhaust duct was centered in the duct and located approximately 6 ft (2 m) downstream from a 90 degree elbow that connected the hood collar with the horizontal exhaust duct that ran between the collar and the exhaust fan.Whenever possible, trained personnel who were
27、 familiar with operation of each appliance were present to supervise the utility connections and to ensure that each appliance was cali-brated and operating normally before any cooking was initiated. INSTRUMENTATIONParticles were captured and classified in the size range from 0.5 to 15 microns using
28、 Marple model 298 personal cascade impactors (PCI) with model 290 IA in-line adaptors. Photographs of the components and an assembled unit are shown in Figure 2. Short sections of copper tubing, 0.183 in. (4.65 mm) I.D., were given a tapered inlet and a 2.48 in. (63 mm) bend radius to form the 90 de
29、gree sampling inlets. The inlet faced downward toward the rising plume. The sampling inlet velocity was 387 ft/min (1.97 m/s) that approximated isokinetic sampling in the plume. Nearly isokinetic sampling was achieved in the horizontal exhaust duct as the centerline velocity and sampling flow rate w
30、ere well known and the sample inlet was sized to provide isokinetic conditions. Table 1. List of Appliances Tested and Corresponding Food ProductsType Cooking Area or Volume Rated Input Food ProductConveyor Broiler 5.5 ft2(0.51 m2) Gas 106,000 Btu/hFrozen one-eighth-pound hamburger patties 10% fat,5
31、5% moistureClamshell Griddle 6.3 ft2(0.59 m2)Gas 70,000 Btu/h electric 11.2 kW Frozen quarter-pound hamburger patties 15% fat,48% moistureConveyor Pizza Oven 15.1 ft2(1.41 m2) Gas 170,000 Btu/hFrozen 17.75 oz 12 in. diameter thin-crustpepperoni pizzasOver-Fired Broiler 5.5 ft2(0.51 m2) Gas 80,000 Bt
32、u/h 5 oz sirloin steaks, 2.0% fat, 72.3% moistureElectric Steamer 13.7 ft3(0.37 m3) Electric 31.1 kW 5 oz boneless skinless chicken breastsMesquite Solid Fuel Broiler 5.5 ft2(0.51 m2) Mesquite charcoalFrozen quarter-pound hamburger patties 10% fat,55% moistureGas Chinese Wok 1.58 ft2(0.147 m2) Gas 9
33、9,000 Btu/h5 oz boneless skinless chicken breasts diced into1 in. cubes with peanut oil128 ASHRAE TransactionsSubstrates used in the impactor stages were 1.34 in. (34 mm) mylar. Final filters were either 1.34 in. (34 mm) PVC membrane with 5 micron pore size or 1.34 in. (34 mm) glass fiber filters. T
34、he impactor that sampled the effluent plume was normally mounted on the end of an EPA Method 5 sampling train. All particles were removed in the impactor so that the EPA Method 5 system received only gases and vapor. The filter in the heated box was removed as it was not needed in these measurements
35、. The exhaust from the impactor that sampled air from the exhaust duct was normally connected directly to a vacuum pump. One set of data for each appliance was obtained by switching the positions of the Method 5 sampling train and the vacuum pump so that the concentration of grease vapor could be ob
36、tained both in the plume and in the exhaust duct. The vapor mass emission results are reported in Kuehn et al., 2009. Particles between 20 nm and 0.8 m in size were analyzed by two Scanning Mobility Particle Sizers (SMPS), one sampling in the plume and one in the exhaust duct. A sche-matic of one of
37、 these instruments is shown in Figure 3. Sampling inlets were fabricated from copper tubing similar to those for the impactors. Approximately 6 in. (150 mm) from the inlet, the sample from the plume was diluted by a factor of 10 with filtered dry air. The diluted sample was then sent to the SMPS for
38、 analysis of the particle size distribution. The sample obtained in the exhaust duct was already sufficiently diluted so it was sent directly to the second SMPS instrument. Each scan over the complete particle size range required approximately four minutes. For appliances with steady emissions, the
39、results provided a well behaved bell-shaped particle size distribution. For appliances with time-dependent emissions such as the clamshell griddle, the scanning results must be averaged over several cooking cycles to provide comparable data.PROCEDUREAfter each appliance was installed and operating c
40、orrectly, several preliminary cooking runs were made follow-ing the appropriate ASTM procedure developed for that appli-ance. The results from these preliminary tests were used to determine the amount of food product to use, the cooking time Figure 1 Schematic diagram of the test facility showing th
41、e location of the gas conveyor broiler and the sample point in the plume.ASHRAE Transactions 129to achieve the desired weight loss and/or internal temperature, and the number of batches or length of cooking needed to capture sufficient effluent for analysis.Each of the impactor substrates was desicc
42、ated and weighed and the dry weight recorded prior to installation into the individual substrate holders and then into the impactor assemblies along with the sampling inlets and clean after filters. Balances included a Cahn C-31 analytic microbalance with a 0-25 mg range and a 0.1 g resolution and a
43、 Sartorius B-120S analytic balance with a range of 0-110g and a 0.1 mg reso-lution. Once the impactors were assembled, they were placed into a desiccator prior to installation in the test kitchen. Install-ing the impactors consisted of connecting one to the end of the Method 5 heated probe and the o
44、ther to a line running to a vacuum pump. The completed Method 5 assembly with the impactor at the front end was then positioned so that the inlet was as close to the center of the effluent plume as possible. An SMPS, dilution air system and data acquisition computer were all located inside the test
45、kitchen opposite the personnel door. The sampling inlet was repositioned slightly from appliance to appliance as the plume center changed location.Sampling from the exhaust duct was accomplished using an isokinetic probe positioned in the centerline of the duct. A second PCI assembly was connected t
46、o a flow-calibrated lami-nar flow meter to determine the correct sampling air flow rate. This was connected to a vacuum pump except the runs where the method 5 sampling train was used to determine grease vapor concentration in the exhaust duct. The SMPS shared the same sampling line with the PCI but
47、 no dilution air was used as the concentration in the exhaust duct was sufficiently low so that dilution was unnecessary.Prior to running a test, the food product was procured and stored at the required temperature. Hamburger patties and steaks were then positioned onto large aluminum trays to enabl
48、e rapid deployment onto the appliance. For the wok, the chicken breasts were cut into cubes and stored in airtight bags. Representative hamburger patties and steaks were preweighed to be able to determine the weight loss. The preweighed food was tracked as the cooking progressed and retrieved separa
49、tely for post cooking weight measurement. Uncooked and cooked samples were also sent to an external laboratory to determine the initial and final moisture and fat content. Once all the instrumentation was positioned and the food product prepared, the exhaust and makeup air systems were turned on. Then the appliance was turned on and allowed to come to operating temperature for at least 30 minutes. For some appliances such as the conveyor broiler, the speed of moving components was checked and adjusted if necessary. At the beginning of each cooking test, all vacuum pumps were turne
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