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Lineal slot ventilator with internal cleaning system and adjustable baffle

Lineal slot ventilator with internal cleaning system and adjustable baffle description/claims

This application claims the priority benefit of U.S. Provisional Application No. 60/938,612, filed May 17, 2007, which is hereby incorporated by reference in its entirety.

1. Field of the Invention

An exemplary embodiment of the invention relates generally to kitchen ventilation systems. Some exemplary embodiments of the invention may be useful in other applications. The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) provides definitions and guidelines for Commercial Kitchen Ventilation (CKV) in Chapter 31 of its Applications handbook. This chapter, entitled “Kitchen Ventilation,” identifies hoods by Type and Style. Based on ASHRAE's definitions an exemplary embodiment of this invention can be identified as either a Type 1 or Type II hood construction, though its primary intended use may be as a Type I hood “used for collecting and removing grease and smoke”. This hood may include grease removal devices such as baffle filters or removable extractors, or both. It may be designed to accept a fixed pipe fire suppression system. An exemplary embodiment of this invention can be used over cooking appliances such as ranges, fryers, griddles and broilers that produce smoke or grease-laden vapors.

2. Description of Known Art

ASHRAE describes the grease removal devices for Type I hoods as 1) Baffle filters; 2) Removable extractors; and 3) Stationary extractors. Stationary extractors are used in water wash hoods and are not removable.

Stationary extractors are cleaned by spraying detergent and 180° F. hot water through a fixed pipe system that is connected from a, typically remote but always separate, water and detergent control panel to the piping manifold connection at the hood. The piping manifold then extends into and throughout the hood extraction chamber and terminates at multiple individual spray nozzles that are precisely located, sized and directed to spray all internal components that may come in contact with grease. These systems may also include pumps and or other flow control devices to facilitate or direct water flow. Due to their complex nature, water wash systems add considerable expense to the hood. Water wash hoods typically cost 2 to 3 times more than identical hoods that do not have these cleaning systems. In addition, the mechanical and electrical complexities of the cleaning systems require sophisticated maintenance not typically available at the restaurant level. Water wash system nozzles also need routine maintenance to prevent them from clogging with grease, as well as a sophisticated siphoning system that injects detergent into the hot water (180°) line. The detergent must then be sprayed through the pipe and nozzle system. The detergent cycle is followed by a hot water rinse. A major national restaurant end-user of water wash hoods reported that its most recent survey found that the majority of its water wash cleaning systems were turned off or not functioning due to lack of, or improper, maintenance.

Due primarily to lower cost and less complicated maintenance conventional baffle filters and removable extractors are the most prevalent methods of grease removal found in kitchen hoods today. They are designed to be removed from the hood for cleaning. ASHRAE recommends the grease removal devices be cleaned “at least daily”. A case-study field trial of an exemplary embodiment was conducted by the applicant and end-user to compare the manual daily cleaning of the extractors versus the daily soak-in-place cleaning system described herein. The trial involved (1) 10′ long backshelf hood with removable extractors installed over (1) 36″ gas griddle and (2) 36″ gas under fired char broilers in a heavy-use fast-casual restaurant. The manual extractor cleaning process includes removing the extractors from the hood and soaking the extractors in a pot sink with a degreasing chemical solution for one hour to loosen the heavy grease. After soaking, the extractors are rinsed and then run individually through the kitchen dishwashing machine. The extractors are then re-installed in the hood. Due to the amount of grease from the extractors the dishwasher must be drained, cleaned and re-filled and pot sinks must be cleaned. This process requires at least one employee and one manager's oversight and consumes 4 man-hours nightly. The amount of water used in the process may be calculated as follows. Although industry standard in size, the extractors require two 24″×24″×18″ deep pot sinks to soak all of the devices simultaneously. At 0.1337 cu.ft. per gallon, the pot sinks require 88 gallons (44 gallons×2) of hot water. The dishmachine is a conventional, small conveyor type, typical in many restaurants, with a wash tank capacity of 23 gallons and a rinse volume of 2 Gallons Per Minute. Assuming a 60 second rinse for each device and a total of six devices, the dishmachine will consume an additional 35 gallons of hot water. For this single 10′ hood, this daily cleaning consumes 132 gallons water or more plus the energy to heat the water, the labor to remove and install the devices and the time required to clean the pot sinks and dishwasher.

This example also helps explain why hood grease removal devices are one of the last items cleaned at the end of the each night. The mess created during cleaning, the cost in time water and cleaners, and the last system cleaned also often leads to neglected cleaning. The neglect increases fire hazard, decreases sanitation and can lead to equipment malfunction and component damage. In many restaurants the daily handling, cleaning and/or abuse of baffle filters and/or extractors causes the devices to become damaged. This damage most often reduces the devices grease removal efficiency which decreases fire safety and of course reduces the useable life of the device.

Food service operators including those operating restaurants are faced with two first-cost hood grease removal decisions. Decision 1 is to increase the cost of the hood substantially by purchasing a hood with stationary extractor and automatic wash system, including the control panel, and sign on to the commitment for expensive more complex life-long maintenance. Maintenance that requires a trained technician not restaurant employees. Decision 2 involves a lower first cost and selects baffle filters or removable extractors that in many operations must be removed, cleaned and reinstalled each day. This cleaning not only shortens the life and effectiveness of the devices but also requires employees and managers who are typically ready to leave the restaurant at the end of their shift to stay in the restaurant long after customers and other employees have left the restaurant. Again this nightly maintenance requires additional time, cleaners, water and the associated expenses.

Regarding heat recovery, in 1996 the Canadian Gas Research Institute published its “Technology Review of Commercial Food Service Equipment”. According to the study, which evaluated facilities and equipment throughout Canada, “Of significance to this study's objective, are the relative low efficiencies (e.g., 10-50%) for standard gas appliances under full load conditions. . . . Part load efficiencies for most appliances can easily be as low as half the full load cooking energy efficiencies . . . . (e.g., 5-10% for gas appliances . . . ).” Even though efficiency improvements have been made, commercial gas cooking appliances continue to waste large quantities of energy by generating heat that is not used in the cooking process and is instead exhausted through the kitchen hood and discharged to the atmosphere. Heat recovery in kitchen hood systems has therefore understandably been attempted in commercial kitchens due to this high energy use and low appliance efficiency. Various plate type exchangers and other air to air devices have been and continue to be used. Unfortunately grease is an excellent insulator and as grease collects on heat recovery devices their efficiency decreases. To maintain efficiency these devices require cleaning systems and routine use of these systems. These systems like the afore described stationary extractor cleaning systems require a separate fixed pipe detergent and hot water system and the associated water, water heating and detergent expenses. Like the stationary extractors cleaning systems these heat recovery systems also require technical support and expensive routine maintenance. The devices typically use aluminum or other light gauge material plates to maximize heat transfer and due to their construction are required to be located away from the hot cooking appliances in duct systems and are most often located on the roof or exterior of the building. Located further from the hood the devices see lower temperature but virtually the same grease loading. The cost to purchase, the lower heat content of exhaust air, cleaning and maintenance costs have greatly reduced the use of these energy saving devices.

FIG. 1 shows an exemplary embodiment of the present invention in a vertical section through a commercial cooking hood and further includes a cooking appliance, exhaust duct and exhaust blower for aid in description of operation.

FIG. 2 shows an exemplary embodiment with airflow through the device indicated by arrows. FIG. 2 also shows the heat recovery chambers in this exemplary embodiment.

• Provisional Patent
• Utility Patent

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