How does radiant heat affect your chef’s and kitchen staff comfort?
Typically, if you tell someone they look “radiant,” you would be complimenting their glowing appearance. If you tell a chef that they look radiant, it probably means they look hot and uncomfortable. Let’s explain how radiant heat affects the comfort of not only your kitchen staff but your chef’s as well.
In the kitchen, when we are cooking, there are multiple heat sources that exist to cook food. Think of griddles, broilers, fryers, combi ovens, etc. Unless it’s induction cooking, a closed-door (like combi ovens) or well insulated process, there’s usually a gross excess amount of heat being produced to cook your food. In a perfectly efficient food heating scenario, the amount of heat produced would be just enough for the piece(s) of food to be cooked and nothing extra. Only heat underneath the food – no additional heat from burner grates or hot pans or griddle surfaces, etc. All the generated heat goes into the food. You could only burn your hand on the food since there wouldn’t be other surfaces that would be unnecessarily heated. Of course, this isn’t reality today. All the extra heat from our current-day cooking techniques require a big stainless hood pulling the excess heat out (and some smoke, effluent) and exhausting it outside. Who wants that heat in their kitchen?
If we are exhausting all that heat outside the kitchen, why does it still get so darn hot and uncomfortable inside the kitchen? In short, much of it depends on the “flavor of heat” you are creating with the cooking equipment. You know, the flavor of heat – like we learned in science class back in school… there are three heat flavors (types of heat transfer): conduction, convection, and radiation. Conduction is easy – that’s where a pot with a metal handle is on a burner and eventually, the handle of the pot gets heated up through the heat energy from the burner to the pot and then into the handle. Convection is what you feel if you put your hand above the heated pot, or over a fire or burner. Radiation is experienced through standing beside a campfire or the heat from the sun; it happens through electromagnetic waves.
Why did I just bore you with horrible flashbacks to 5th grade science class? Because radiant heating is a big deal. It is often one of the major contributing factors for an uncomfortable kitchen – or at least an uncomfortable person in the kitchen, according to the sweaty chef.
In some cases, the hood could be doing a poor job of taking out the convective heat component of the cooking processes. If there isn’t enough cfm (cubic feet per minute) for the hood to get all that extra heat exhausted and it ends up spilling out of the hood and into the kitchen, then that is an issue.
Let’s assume we have that part of the equation covered, and the convective heat is being fully removed. The remainder of the heat coming from the appliances is radiated heat, which travels by line-of-sight from the hot object/surface/equipment to the next object in the room. Nearby is a chef who may be wearing a black smock, too, which only increases their discomfort. With some of these processes, there’s a large amount of radiant heating that comes from the appliance. The bigger (surface area) and hotter the surface is, the more prone to provide radiant heating. The person working in front of an underfired charbroiler has very little option but to be hot. That large heated surface (around 700 degrees) will be sending electromagnetic waves (same as the sun’s rays) toward them and heating them up. Even in a nicely cooled 70 degree surrounding kitchen, they will absorb that heat and feel the physical impacts. White (lighter colors) help reflect much of this radiant heat, while black (darker colors) absorbs more of it and will make you warmer. By simply changing outfits, the chef would drop their temperature significantly!
This radiant heat can’t be taken out by the hood, even if you increase the exhaust cfm all the way up – and then increase it even more. Radiant heat doesn’t follow the smoke and effluent; it travels through the medium of air and finds a surface/body to hit and then heats it up. This means the chef gets hot, as well as other items in the kitchen that are within proximity of the heat source. When these other surrounding items heat up, they provide added convective heat loads in the kitchen that the HVAC must offset. The engineering team that designs the HVAC system must consider this radiant load in the space in their cooling calculations. Accepted practice is to account for the radiated load from appliances when calculating the cooling capacity required to offset it.
A poorly constructed hood without proper air space or insulation between its interior and exterior skin can be the worst culprit in heating up the kitchen space. It’s a metal box that is heated from the cooking and then, once heated, radiates that heat to all surrounding surfaces/bodies in the kitchen. Therefore, it is good practice to have a well-engineered hood that can minimize this impact in the space, making it more comfortable and reducing the HVAC size and energy use.
Ironically, if you talk to the sous chef on the other side of the cook line, far away from the heat of the charbroiler, working in front of a bank of well-insulated combi ovens, they’ll tell you it’s perfectly comfortable in the kitchen. You shouldn’t tell them that they look radiant, though.
Regional Sales Manager, Halton Company
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