Regardless of the type of equipment to use, whether they are electrical or gas fired ovens, there are three critical elements to consider. These include heat-up, soak time, and cool-down time. In terms of heat-up, the oven needs to have sufficient heating capacity to be able to bring the product to the desired temperature with a specified time. Also, the heating capacity of the equipment must be greater than the energy required just to heat the product being processed to compensate for the heat losses during the process. And finally, the product should be able to absorb heat at a rate sufficient enough to reach the desired temperature within the specified time frame.
For the soak time, it refers to the time required for the product to reach the desired process temperature within the desired time frame. In order for the temperature to remain at the desired level, a programmable controller is used. Only then the cool-down process may begin to complete the entire cycle. For most applications in gas fired ovens, the soak cycle starts only when the desired time for the heat-up has finished. In case a more precise control is required, a guaranteed soak method can be used. Under this option, the controller can set the timer for the soak cycle only when the set point temperature has been reached.
Now for the last important element, the cool-down time, the considerations for cool down rates are quite similar to heat-up rates requirements. Usually, in gas fired ovens, the cool down is attained by exhausting the heat from the equipment wherein the cooler, ambient air enters the oven, replacing the warm air inside.
In case the cool down rate has to be controlled, there are two ways to do it. One is with the exhaust dampers being opened to their optimum position while the heaters provide sufficient heat to prevent the temperature from dropping down too quickly. The other alternative is by controlling the modulating dampers which modulate to keep the cooling rate. Both of these options would help achieve the right cool down rate.