Labyrinth air flow calorimeter

The rate of isothermal heat evolution in lignocellulosic sheet material was studied at temperatures between 150 and 230°C using a labyrinth air flow calorimeter and commercial hardboards, medium density boards and laboratory hardboards of holocellulose, bleached kraft and groundwood, the latter with and without fire retardants. 

Such basic data are here presented from isothermal measurements on 5 by 90 cm lignocellulosic and cellulosic strips up to 13 mm thick. A suitable labyrinth air flow calorimeter operating at temperatures up to 250°C was built for these fairly large size samples. (7)... 

Figure 1. Labyrinth air flow calorimeter. Cross section A - A shows the measuring channel with four samples and the two outer insulating labyrinth channels. Cross section B - B shows one of the two piles of thermocouples which are placed at the channel inlet and the outlet to record the air temperature difference. (Reproduced with permission from ref. 10. Copyright 1989 De Gruyter.)...

The design and necessary calculations for the labyrinth calorimeter with turbulent air flow but low heat losses, have been presented earlier (7). See Figure 1. The advantage over micromethods such as DSC is that effects of sheet density and caliper of fiber entities... 

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