Let's Get Kit STarted

Project undertaken in course year 2022-23 with Kit Switch

Project Goal

Characterize how to implement ducting that guides contaminated cooking air from a pre-fabricated Kitchen cooking module called Kit Cook, to a building's pre-existing exhaust outlets. The Kit Cook module is to be retrofitted into pre-existing office buildings that are being renovated for residential use; the building will have pre-existing exhaust vents that the Kit Cook module needs to vent, but the location may be far away.

Project Motivation

Affordable housing is an existential threat to tens of millions of Americans. Retrofitting old, safe buildings otherwise scheduled for demolition is an effective solution to mitigate this problem, but current methods to furnish such buildings for habitation are expensive. If kitchens, the most expensive component of retrofitting, can be modularized and thereby cost-optimized, affordable housing via retrofitting will become an attractive option for developers.

Kit Switch is developing modular systems to place kitchens into these retrofits, and the placement of the kitchen doesn't always align with where the existing exhaust is, so understanding what can be achieved with ducting to be code-compliant is important in the design of these homes.

Background

To meet federal and California code, the ductwork must retain a minimum airflow rate. The complexity of a ductwork configuration, determined by the duct length, duct diameter, and number of bends, can increase the back pressure and reduce the airflow rate of a system. Back pressure is the resistance, or force, opposing the desired amount of airflow through a pipe.

Currently, there is no publicly available performance chart outlining the relationship between back pressure and airflow for the selected range hood, thereby motivating this project. Given the variability in the spaces in which Kit Switch intends to install their products, our project focused on determining the constraints for code-compliant ductwork configuration in any room layout.

Schematic of simplified plan for the Kit Cook module to implement a range hood, fan, and duct to an outside wall that exhausts air.

High Priority Requirements

Execute 6-inch round duct design extending up to 20 feet where elbows will not hinder the pump strength of the ventilation hood
Per California Code, ductwork supports at least 100 CFM of airflow at the exhaust
Ductwork must be made of metallic material
The system cannot experience leakage of more than 10% of total airflow
Horizontal ducting shall be supported at no more than 4-foot intervals, and horizontal deflection shall not exceed 0.5 inches.

Ethical Considerations

Responsibly sourcing sustainable materials, since not doing so would leave a carbon footprint equivalent to that of a conventional kitchen
The project brings socio-economic benefits, where the Kit Switch's products may contribute to the revitalization of city districts

Solution

We developed the "Kit Check" tool for users to reference in the design and installation of the ventilation system for the Kit Cook Module. The user inputs the desired duct length, number of desired bends, duct diameter, and airflow generated by the hood; Kit Check determines the back pressure, and whether there will be at least 100 CFM, at the exhaust. All our measures were physically tested to validate the tool.

We developed the "Kit Guide" handbook for installers to reference for using Kit Check and understanding best practices of installation.

Schematic for testing

Schematic showing test setup for assessing back pressure and flow rate of the ductwork system. A manometer measured back pressure from a pierced hole near the ductwork inlet, an anemometer measured the flow rate at the outlet

Test setup showing the most bends

Many different combinations of duct length and bends were built to test the back pressure and outlet flow rates. This figure shows the configuration with 20 feet of ducting and seven 90-degree bends

Measuring air flow

Anemometer being used to measure air flow at the outlet of the range

Validation scenario 1

Top: Schematic for the layout "Geary 1" used to validate the tool; the planned ductwork is drawn in yellow

Bottom: duct system built to measure the pressure and flow rates for Geary 1.

Validation scenario 2

Top: Schematic for the layout "Geary 2" used to validate the tool; the planned ductwork is drawn in yellow.

Bottom: duct system built to measure the pressure and flow rates for Geary 2.

CFM data on existing fan

The performance chart for the DC Centrifugal fan that resides within the Range Hood. Note that this chart is on the fan itself, but no data existed for the fan in the range hood. So the team built that data with various duct configurations (next chart)

Test Results on different configs

Test results (in red) of the various duct configurations the team built, when connected to the range hood. These ranged from 0 bends to 7 bends, and varying duct lengths between them.

Test Results on validation scenarios

Results for Gear 1 (blue) and Geary 2 (green) placed on the data chart. Data shows that Geary 1 and Geary 2 both fall on the chart, AND achieve greater than 100 CFM outlet flow rate, so meets the requirement.

Kit Check system view

Kit Check layout, where users will be able to insert the length they need in the first row, and the number of bends they estimate will be needed in order for the Kit Cook module to be placed in the residential unit. Users may modify the entries outlined in green.

Other work conducted

Deflection testing
Leakage testing

Student team

Future Work

Enhance the prediction tool by more accurately quantifying pressure losses that result from dampers, vents, grills or filters.
Gather feedback from installers on both the Kit Check and the Kit Guide
Ducting system to be built into the Geary facility, and compare results from that implementation to lab testing results

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