Linear Combustion Calorimeter

Linear Combustion Calorimeter


Thermoelectric Linear Combustion Calorimeter
Applied to the Smoking Process

The purpose of this calorimeter is to measure that fraction of heat from a burning cigarette inhaled by a smoker versus that fraction rejected to the outer world through the mechanisms of radiation and convection.

To separate both thermal transport mechanisms, the thermoelectric wall calorimeter, which detects and integrates all heat transfer modes, is employed to measure only radiation and convection from a non-contact, combusting cigarette. This is defined as that fraction of heat which is rejected externally to the outer world. The thermoelectric calorimeter is designed as a cylindrical chamber with internal heat flux sensing surfaces which encompass, but not contact the burning cigarette. This system is entirely analogous to that thermal process taking place during smoking in the outer air.

The absorptive loss, or the heat ingested by the smoker in the form of heated gases is simultaneously measured by the rise in temperature of the gas drawn through the cigarette, the known gas flow rate, and the known specific heat of the gas.

In operation, a variable speed air pump whose flow rate can be adjusted to that taken by a smoker during an average “puff” draws in air which is initially measured by a high response, electronic flow meter. The air is conducted through a heat exchanger which, in turn, is immersed in a constant temperature bath where the gm temperature is measured prior to entering the thermoelectric calorimeter. The prime purpose of the constant temperature bath is to ensure that no additional heat is added to, 0, removed from the gas during the combustion process. As indicated, the thermoelectric cavity contains the ignited cigarette; this cooled cavity absorbs the heats of convection and radiation, but not the heated gas which is removed through the cigarette. Immediately is displayed upon a 0 1 % accurate digital meter in terms of Degrees Centigrade. The gm flow rate is also displayed upon a digital meter i. terms of Liters/minute. A separate digital meter displays the output from the thermoelectric calorimeter in terms of wafts. This visual display enables sufficient data to be taken to determine the relative output of any cigarette being tested. The outputs of each readout have been configured to provide appropriate signals to a computer together with recommended software.

As predicted, preliminary measurements made with cigarettes indicate that the quantity of heat drawn into smokers lungs is a small fraction of the total heat of combustion.