1、702 ASHRAE TransactionsThis paper is based on findings resulting from ASHRAE Research Project RP-1480.ABSTRACTThe objective of ASHRAE Research Project RP-1480 wasto expand the database for the capture and containmentrequirements of island canopy hoods. The study investigatedthe performance of four i
2、sland canopy hood configurationsover standardized cooking equipment lines including: (1) a 4 ft(1.22 m) rear filter single-island, (2) a 6 ft (1.83 m) V-banksingle-island, (3) an 8 ft (2.44 m) double-island, and (4) a 10 ft(3.05 m) double-island hood. More than 200 configurationsand/or conditions we
3、re tested, including the evaluation of sidepanels, hood partitions, replacement air strategies, andreplacement air temperatures. This paper provides an over-view of the capture and containment performance for the twodouble-island canopy hoods. This research project showedthat the performance of a do
4、uble-island canopy hood iscomparable to a back-to-back wall-mounted canopy hood fora given duty class of appliances as long as the replacement airsupply and/or cross drafts do not impede capture and contain-ment. Large appliance overhangs and well-balanced, low-velocity replacement airflow are criti
5、cal for optimizing theperformance of double-island canopy hoods.INTRODUCTIONDouble-island canopy hood styles are typically specifiedin larger commercial and institutional kitchens. The construc-tion of a double-island hood is essentially two wall-mountedcanopy hoods placed back-to-back (without a di
6、viding wall).Because of this similarity, one objective of the research projectwas to determine if the capture and containment performanceof double-island hoods was comparable to wall-mountedhoods (on a per linear foot basis). While the performance data-base for wall-mounted canopy hoods has become m
7、ore robust(Swierczyna et al. 2005, 2008; PG (2) investigate the benefit of hooddesign features such hood depth, appliance overhang, sidepanels, and hood partitions; and (3) investigate the impact ofdifferent makeup air scenarios. While this technical paperfocuses on the double-island canopy hood, th
8、e single-islandcanopy hood evaluation is reported in the technical papertitled, Capture and Containment Ventilation Rates for Single-Island Canopy Hoods (Sobiski et al. 2010). The complete dataset for both hood types can be found in the final report forASHRAE Research Project 1480 (Swierczyna et al.
9、 2010a).Threshold capture and containment exhaust airflow ratewere determined in accordance with ASTM F1704-05, Stan-dard Test Method for Capture and Containment PerformanceCapture and Containment Ventilation Rates for Double-Island Canopy HoodsRichard T. Swierczyna Paul A. Sobiski Donald R. Fisher,
10、 PEngAssociate Member ASHRAE Member ASHRAE Associate Member ASHRAERichard T. Swierczyna is a research engineer and Donald R. Fisher is president and CEO at Fisher-Nickel Inc., San Ramon, CA. Paul A.Sobiski is a research engineer at Architectural Energy Corporation, Schaumburg, IL. LV-11-005 (RP-1480
11、)2011. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE
12、S prior written permission.2011 ASHRAE 703of Commercial Kitchen Exhaust Ventilation Systems (ASTM2005). Capture and containment was validated using twoschlieren systems and two shadowgraph systems, which allowreal-time visualization of the thermal and cooking plumes(Schmid et al. 1997). For each per
13、formance evaluation, simu-lated heavy-load cooking was used. The simulated cookingperformance of the appliances was calibrated at the beginningof this research project to represent the actual cooking plumegenerated during the cooking process (Swierczyna et al.2005). The actual cooking conditions wer
14、e done in accordancewith the appropriate ASTM performance test methods(ASTM 1996, 1999a, 1999b).EXPERIMENTAL DESIGNLaboratory LayoutThe existing commercial kitchen ventilation (CKV) labo-ratory (Swierczyna et al. 2003) was modified to accommodatethe large-island canopy hoods and the anticipated incr
15、ease inexhaust airflow. The seven existing floor-mounted displace-ment diffusers were complemented by an additional sevendiffusers along the opposite wall, providing up to 9000 cfm(4250 L/s) of conditioned replacement air in a parallel config-uration. Two air-handling units supplied the local makeup
16、 airdevices, with a maximum capacity that varied greatly based onsystem static pressure. The exhaust hoods fan had a maximumcapacity of 9600 cfm (4530 L/s). To quantify the air suppliedto the laboratory, individual airflow measurement stationswere installed before the two displacement ventilationbra
17、nches and before each local makeup air device. A plan viewof the HVAC layout for the double-island hood setup is shownin Figure 1. An immediate observation is just how much of the labo-ratory space was occupied by the large double-island hood andassociated local replacement air plenums and diffusers
18、. Whenthe research proposal was developed, the research team hadrealized that the double-island canopy hood configurationswould take up a significant portion of the available floor spacewithin the lab. However, since cooking equipment and hoodsare often shoehorned into small kitchens, it was felt th
19、e testdata would be representative and relevant. In hindsight, wemay have underestimated that impact that this cramped testsetup had on the experimental protocol. Even in a small, real-world kitchen with double-island hood, replacement air can besupplied from all four sides of the hood. For this pro
20、ject,supplying 9600 cfm (4530 L/s) of replacement air from onlythe front and back of the hood may have created an unrealisticenvironment, particularly with respect to evaluating the bene-fit of end panels and dividing partitions.Airflow VisualizationFocusing schlieren and shadowgraph systems were th
21、eprimary tools used for airflow visualization. Schlierensystems visualize the refraction of light due to air densitychanges. Using sophisticated optical technology, the labora-tory schlieren flow visualization system amplifies this effectfor lower temperature differences, providing higher sensitivit
22、yand contrast than what is seen by the naked eye (Schmid et al.1997). Shadowgraph systems also make use of the schliereneffect, providing similar sensitivity but with less contrast thanschlieren flow visualizationsystems.The layout of the opticalvisualization systems for the capture and containment
23、evalu-ation is shown in Figure 2.In addition to the focusing schlieren and shadowgraphsystems, theatrical fog distributed through tubular manifoldswas used to visualize the appliance thermal plume near thecooking surface. This method was especially useful for eval-uating the effect of local makeup a
24、ir diffusers on the thermalplume, as the theatrical fog would trace the plume as it wasforced horizontally and/or downward. An example of theFigure 1 Layout of supply air systems for double-island hood.704 ASHRAE Transactionssmoke manifold in use with the single-island hood setup isshown in Figure 3
25、. Hood SpecificationsThe two double-island hoods were 10 ft long by 2 ft high(3.05 by 0.61 m), and were installed with the lower edge of thehood 78 in. (1.93 m) above the finished floor. The depth of thehoods varied from 8 to 10 ft (2.44 to 3.05 m). Note that thesides of the hoods were transparent s
26、o that the schlierensystem could view the thermal plume within the hood reser-voir. To represent a generic application, the island hoods didnot have performance-enhancing features such as flanges orinterior geometric elements. Each hood had an open hem onthe left and right side to accommodate mounti
27、ng side panels. Double-Island 10 by 8 ft (3.05 by 2.44 m) CanopyHood. The 8 ft (3.05 m) deep double-island canopy hoodFigure 2 Visualization systems for hood capture and containment performance evaluations.Figure 3 Smoke manifold used to evaluate the performance of single-island hood. 2011 ASHRAE 70
28、5comprised two 4 ft (1.22 m) deep rear filter canopy hoodsplaced back-to-back. The hood was equipped with twelve 19.6by 19.6 by 1.8 in. (500 by 500 by 50 mm) baffle-type greasefilters, and exhausted through two 36.0 by 14.0 in. (910 by360 mm) exhaust openings. The hood setup over a heavy-dutyfront l
29、ine and light-duty back line is shown in Figure 4.Double-Island 10 by 10 ft (3.05 by 3.05 m) Canopy Hood. The10 ft deep (3.05 m) double-island canopy hood was fabricatedby extending the front panels on the 8 ft (2.44 m) island canopyhood by 1 ft (0.30 m). The hood was equipped with 12 19.6 by19.6 by
30、 1.8 in. (500 by 500 by 50 mm) baffle-type greasefilters, and exhausted through two 36.0 by 14.0 in. (910 by360 mm) exhaust openings. The hood setup over the mixed-duty line front and back is shown in Figure 5. Side Panel and Partition SpecificationsThe effect of a tapered side panel and center part
31、ition wasinvestigated on both of the double-island hood configurations.Side panel #1 was a tapered side panel, which measured43.0 in. tall, 84.0 in. wide at the top, and 57.0 in. wide at thebottom (1090 by 2130 by 1450 mm). A steel partition wasinstalled in between the two appliance lines. It measur
32、ed43.0 in. tall by 119 in. wide (1090 by 3020 mm). It droppedabout 2 in. below the cooking surface of the broiler. Theseaccessories are shown in Figure 6.Makeup Air SpecificationsDisplacement Diffusers. Maintaining a zero-pressuredifferential between inside and outside the laboratory, replace-ment (
33、makeup) air was supplied at an equal volume to theamount of air being exhausted through the hood. For the base-case configurations, 100% of the replacement air was suppliedthrough 14 floor-mounted displacement diffusers. When alocal makeup air strategy was being investigated, the differ-ence between
34、 the local makeup airflow and exhaust airflowwas delivered to the room through the displacement diffusers.The diffusers were balanced left-to-right across each system,and each system was then balanced to ensure balanced airflowfrom both sides of the laboratory. The intention was to providea low-velo
35、city air supply, minimizing the influence that thereplacement air has on hood performance. To create a condi-tion of unbalanced replacement air within the laboratory, therear diffusers were used as an exhaust system. This test config-uration was designed to emulate a kitchen design wherereplacement
36、air was not provided between the island canopyand second hood in the kitchen. In other words, exhaustingthrough the displacement diffusers created a negative pressuresituation similar to having second exhaust hood at the rear ofthe island canopy hood. Ceiling Diffusers. Two four-way ceiling diffuser
37、s andtwo perforated ceiling diffusers were used as part of the localmakeup air investigation. Each diffuser was 24.0 by 24.0 in.(610 by 610 mm), was connected to a 12.0 in. (305 mm) diam-eter duct, and was mounted 8.0 ft (2.44 m) above the floor.One diffuser was centered on the right side of the hoo
38、d, in-linewith the filter bank and 24.0 in. (610 mm) from the side of thehood. Another diffuser was located at the front of the hood,with the center of the diffuser located 24.0 inches (610 mm)from the right side of the hood and 24.0 in. (610 mm) from thefront of the hood. Gaps between the hood and
39、diffusers werefilled in with either a suspended ceiling or a disabled perfo-rated perimeter supply. Test conditions included alternatingthe operation between the two types of diffusers and betweenthe two locations.Figure 4 Setup of double-island 8 ft (2.44 m) deep canopyhood.Figure 5 Setup of double
40、-island 10 ft (3.05 m) deep canopyhood.706 ASHRAE TransactionsPerforated Perimeter Supply. Four perforated perime-ter supply (PPS) plenums were tested within the scope of thelocal makeup air investigation. Each was 12.0 in. deep by6.0 in. tall (305 by 150 mm), with 10.0 ft (3.05 m) of activePPS acro
41、ss the front and rear of the hood and 8.0 ft (2.44 m)of active PPS along the left and right sides of the hood, for boththe 8 and 10 ft deep hoods. The PPSs were located adjacent tothe hood, along the front, rear, and side panels.Airflow through the four PPSs was balanced using thefactory louvers and
42、 additional dampers at the two 14.0 by10.0 in. (710 by 255 mm) inlets to each PPS. The air velocityfrom the face of each PPS was measured with a 4.0 in. (100mm) rotating vane anemometer at three airflow rates. Eachreading was an average of two single-point measurementslocated at the center of 1.0 ft
43、2(0.09 m2) areas along the PPS,with the anemometer held at a distance of 2.0 in. (50 mm) fromthe face of the PPS. Two specific airflow rates were used for the PPS duringthe project. The low-flow setpoint was 80 cfm/ft of PPS(124 L/s/m) or 2240 cfm (1057 L/s) total airflow. The high-flow setpoint was
44、 160 cfm/ft of PPS (248 L/s/m) or 4480 cfm(2115 L/s) total airflow.Appliance Specifications and CalibrationThe cooking appliances selected to challenge the exhausthoods under test included an underfired gas charbroiler fromthe heavy-duty class, a gas fryer from the medium-duty class,and a full-size
45、electric convection oven from the light-dutyclass (ASHRAE 2003b).The appliances were calibrated according to ASTM Stan-dard Test Methods (ASTM 19952004). The two-vat fryersand broilers each operated at equivalent ASTM full-load cook-ing conditions, and the full-size convection ovens used iceloads to
46、 cause continuous element operation. Then, simulations were established using the laboratorysvisualization systems to ensure a consistent effluent plumebetween actual and simulated cooking conditions, which wasconsistent with prior research during ASHRAE ResearchProject RP-1202 (Swierczyna et al. 20
47、05). Simulation of theASTM-specified cooking conditions was achieved for thefryers by using a calibrated water boil with an input of 40,750Btu/h per fryer to generate a thermal plume that matched theplume from cooking french fries. Simulated cooking for thebroilers was achieved by simply increasing
48、the gas pressure tothe burners to 65,000 Btu/h, which produced a thermal plumeof volume and strength that matched the plume from cookinghamburger patties. Since there was no difference in requiredexhaust rate for the 12 kW full-size electric convection ovenduring idle and cook conditions, the ovens
49、were idled duringtesting. This simulated cooking strategy greatly improved test-ing by creating a constant effluent challenge, improvingrepeatability and reducing laboratory time and product cost.Appliance/Hood RelationshipsThe horizontal distance from the edge of the hood to theedge of the appliance is referred to as hood overhang. Whilethis may seem to be a straightforward measurement, variationsare possible. At the appliance, the overhang can be measuredto the cooking surface or to the vertical surface of the appli-ance. At the hood, the overhang can be measured to the outsideedge of
