Preliminary investigation of temperature and pressure profile of pudam in the preparation of Siddha medicine Padigara parpam

BACKGROUND: Pudam is one of the manufacturing processes used extensively in preparing parpam and chenduram in the Siddha healthcare system. The scientific understanding of the process is not fully understood. OBJECTIVE: In this work, our objective was to investigate the temperature and pressure profile of the pudam process and also to understand the porous nature and low thermal conductivity of the sealed agal (Earthen vessel) used by replicating the traditional manufacturing process of Padigara parpam medicine in a pit. MATERIALS AND METHODS: The temperature and pressure profiles were recorded. The size and mass of the cow dung cakes required to conduct the pudam process were discussed. The agal's porosity, thermal conductivity, and thermal diffusivity were experimentally determined. The pressure test of an empty agal was performed in an electric kiln and a pit to find the pressure development inside it and understand the sealed agal's role. RESULTS: The maximum temperature of the pudam process was recorded as 807 °C, and the maximum heating and maximum cooling rate were calculated to be 30 °C/min and 8 °C/min, respectively. The holding time was found to be 66 min above 600 °C and 51 min above 700 °C. The maximum pressure built during the pudam process was 8.2 mbar. CONCLUSION: The test results indicate that the bottom location of the sealed agal is the optimum place to record the temperature of a pudam process. The sealed agal does not allow pressure to build inside, and the pudam process can be considered a heating process that occurs at atmospheric pressure. Increasing the quantity of cow dung cakes for the exact size of the sealed agal and pit increases the raw material's temperature and holding time and reduces the maximum heating rate.