Gas Application Technologies (Commercial, Industrial
Use)
Commercial & Industrial Energy Business Unit
Objectives
In the case of gas-fired cooking equipment, Japanese law requires an exhaust flow rate that is 40 times as high as the standard rate for the theoretical combustion gas amount.
On the contrary, for electric-heating cooking equipment, there is no legal regulation concerning exhaust flow rate.
As a result, kitchens equipped with electric-heating cooking equipment are often designed with an exhaust flow rate of less than half the amount required for gas-fired cooking equipment.
This is based on some reports that typically state something like, "electric-heating cooking equipment requires a lower exhaust flow rate than gas-fired equipment to discharge cooking contaminants such as oil smoke."
This is the correct conclusion under the condition that there is no air disturbance in the kitchen.
However, in reality, the air in commercial kitchens is disturbed by cooking operations and air conditioning, and by air that enters through open windows and doors.No research conducted before on the necessary exhaust flow rate in commercial kitchens took these actual kitchen conditions into consideration.
Therefore, Osaka Gas jointly conducted research with Osaka University (Environmental Engineering Research Office, Construction Engineering Program, Engineering Research Course, Graduate School).
Using both gas and induction-heating cooking stoves with the same cooking capacities, we studied the capture efficiency of cooking contaminant effects by taking into consideration the air disturbances caused by air conditioners and the movement of cooks.
Experiment Method
The cooking equipment was operated under the conditions shown in Fig. 1 and Table 1.The contaminants produced by cooking were measured using a tracer gas (SF6). The cooking contaminant capture efficiency was calculated from the concentration of tracer gas (SF6) which was generated from a saucepan on the stove or from the internal edge of the oil pan in the case of a fryer. The amount of the substance generated was calculated from the contaminant concentration when using an enclosure attached to the hood. (Fig. 1)
External air disturbances were generated by the following methods:
- a side draft generator which produced an airflow of a constant velocity was placed on the left side of the cooking equipment to represent the air disturbance caused by an air conditioner (Fig. 1), and
- a dummy (a mannequin) was moved at a constant speed (3.6 km/h) in front of the cooking equipment to simulate the air-disturbing movement of a cook (Fig. 2).
< Test conditions >
| Cooking Stoves | Fryer | ||
|---|---|---|---|
| Basic requirement | Same pot heating capacities | Same oil contact surface areas in pots | |
| Testing condition | Continuous boiling of water in 36-cm sauce pan | Standby (oil temperature; 170-185°C) During frying of potatoes (oil temperature: 170-185°C) |
|
| Natural gas | Heating power | 14.5kW (12,500kcal/h)*2 | 11.6kW (10,500kcal/h)*2 |
| Induction heating | Heating power | 5KW*Q | 5KW*Q |
| Exhaust flow rate | 540-1620m3/h | 440-1320m3/h | |
| Exhaust hood dimensions | W1200*D750*H640mm Floor surface to bottom hood surface: 1,860 mm |
||
< Testing facility >
(Fig. 1)Diagram of test equipment and side draft generator
(Fig. 2)Moving dummy test equipment
Test Results
- Effects of air currents inside kitchen
The flow of the cooking exhaust was visually confirmed with smoke generated by a smoke machine.[ Flow of cooking exhaust without air disturbance ]
When there were no air currents in the kitchen, the exhaust flow rate required to remove the cooking contaminant was less with the induction-heating cooking stoves than the gas-fired one.
[ Exhaust flow in the case of a side draft ]
With the induction-heating cooking stoves, even a weak side draft caused the cooking contaminant to move outside the exhaust hood.
- Result of capture efficiency
[ Capture efficiency of cooking stoves ]
- Effect of cook's movement
To simulate the movement of a cook in a commercial kitchen, a dummy was moved in front of the cooking stoves, and the capture efficiency of the cooking contaminant was examined. (Dummy moving speed: 1.0 m/s (3.6 km/h), distance from ranges: 300 mm)
Click here to see a GIF animation of the effect of dummy movement.
Click here to see the moving image of the effect of dummy movement.
< Conclusion >
Based on the above experiments results, it was confirmed that, when induction-heating cooking equipment was used in a real commercial kitchen where the room air was disturbed, oil smoke or other cooking contaminants were not fully removed by the exhaust hood if the exhaust flow rate was less than that of gas-fired cooking equipment at the same cooking capacity.
