Deep fat fryer

DETAILED DESCRIPTION Methods and apparatus are herein disclosed for substantially isothermal heating of a vat containing cooking liquid, such as deep fat frying oil.
The apparatus uses a mechanism sometimes known as the heat pipe principle to provide the desired temperature uniformity by employing one or more surfaces of the vat itself as the heat pipe condenser.
The oil is thereby heated by an essentially isothermal surface, and the formation of hot spots, or relatively hot zones is minimized, and may for all practical purposes be considered to be substantially eliminated.
Particles of food materials and the like that adhere to the vat walls will not result in oil breakdown because, as a covered spot on a wall becomes insulating, it accepts less and less vapor condensation from the heat pipe, and it accepts, therefore, less and less heat energy.
The temperature cannot rise above the condensation temperature of the isothermal vapor.
The fact that heat is not being transferred away from the spot is no longer important because heat transfer to the spot is reduced.
Normal cooking oil such as, for example, cottonseed oil, other vegetable oils and animal fats can be used for long periods of time without developing a rancid odor or taste which will occur in conventional direct immersion heating equipment.
With the risks of hot spots out of the way, it is now possible to transfer heat at maximum heat flux from the entire heat transfer surface, namely the walls of the vat, to the cooking oil.
This facilitates quick recovery.
The amount of oil which is absorbed by the food in deep fat frying appears to be related inversely to the oil temperature.
When prior deep fat frying apparatus is used and cold food is placed in the oil, the temperature of the oil drops and a relatively large amount of oil absorption occurs before cooking temperature is recovered.
On the other hand, in the methods and apparatus of the present invention which employs essentially isothermal transfer of heat to the oil at a desired working temperature uniformly over the entire heating surface, rapid heat transfer to the oil is enhanced so that the temperature of the oil does not drop as far as in prior apparatus and recovers more quickly