Review of the Characteristic Curves of Silkworm Cocoon Hot Air Dryingand Its Technological Configuration

To pass on Chinese cocoon-drying technology to developing countries, this paper reviews characteristic curves of silkworm cocoon hot air drying and its recent research advances in cocoon-drying technology in China based on the epochal and regional characters of cocoon drying technology development. (1) Three characteristic curves of cocoon drying are systematically explained, each of which can be divided into preheating, constant speed, and deceleration stages. The temperature susceptibility (i.e., the characteristics of response to temperature conditions) curve of the pupa successively shows heating, constant temperature, and heating processes. (2) Changes in the drying speed and temperature susceptibility of a fresh cocoon layer and naked pupae were examined in detail before and after pupae were killed in the preheating stage. It is proposed that heating the cocoons as soon as possible during the preheating stage of cocoon drying improves the work efficiency and cocoon quality. (3) The effects of the temperature and humidity of the hot air on the cocoon drying speed (i.e., speed coefficients) are obtained using the enthalpy psychrometric chart. The parameter configuration of cocoon drying technology is elaborated according to the speed coefficients in combination with the characteristic curves of cocoon drying and the influence of the laws of cocoon drying technology on cocoon quality. Furthermore problems in the technological configuration and the direction of future development are noted.