Study On The Speciality Of Heat And Moisture Transfer In Hardy Plant Roots

The cold tolerance of plant has developed into a comprehensive multidisciplinary research. In the present thesis, the conventional research methods of "theoretical modeling-simulation-experimental verification" are used to study on the speciality of heat and moisture transfer in hardy plant roots, with Common Camellia roots as research objects. Theoretical analysis is first conducted with heat and mass transfer processes within and between roots and surrounding environment. The equations of plant heat and mass transfer are then derived. Three-dimensional physical model of Common Camellia root is established on the base of mastering plant physiology, to simulate the temperature distribution and fluid flows in certain circumstances. The rules of physical parameters and the changes of temperature within the roots are determined by experiment for different environment temperature.The rules of physical parameters within the roots are determined for different environment temperature and the measured dates are fitted and analyzed, with Common Camellia as the main research object, Nex latifolia thunb and Pinus as validation group, a non-hardy plant Flowering Cherry as a control experimental group. The results show that:In the experimental temperature range, as to handy plants’roots, there is the same law of specific heat with environment temperature, but the heat value and peak have great differences; Thermal conductivity of hardy plants at the roots above 0 ℃ changes little with increasing temperature, while below 0℃ increases rapidly with decreasing temperature; As to non-handy plants’ roots, the specific heat increases like a quadratic function with increasing temperature, the thermal conductivity of volatility is little; Both of these two parameters of handy plants’roots are basically higher than that of non-hardy plants.The changes of temperature within the roots of Common Camellia and Flowering Cherry are determined by experiment for different environment temperature. The results show that:As to Common Camellia roots, there is the same variation trend with soil temperature, but each point temperature is lower than the corresponding ambient temperature. Indicating that the roots are greatly influenced by the ambient temperature, and there is lag; In the axial direction, temperatures of Common Camellia root gradicntly distribute with depth; In the radial direction, temperature distribution of each point is Tn-2> Tn-3> Tn-4> Tn-1(n=1,2); By comparing the temperature within the roots of Common Camellia and Flowering Cherry under the same environmental conditions, cold resistance mechanism of plant is indirectly analyzed.Theoretical analysis is first conducted with heat and mass transfer processes within and between roots and surrounding environment. The equations of plant heat and mass transfer are then derived. Three-dimensional physical model of Common Camellia root is established on the base of mastering plant physiology, to simulate the temperature distribution and fluid flows in certain circumstances. The results show that:Under the combined effect of the convective heat transfer of fluid flow and heat conduction of plant roots, the temperature reaches a stable gradient that decreased from down to up, and the temperature difference between each part is larger; The temperature of the sapwood is higher than that of the phloem, and the temperature of sapwood flow drops in the flow process, while that of phloem flow rises in the flow process; There is a very slow flow stream only in phloem and sapwood of plant root, which has a close connection with weak physiological metabolism at low temperature and transpiration effect, as well as consistent with the flow state of porous media; The law of simulated values is the same as that of measured values, which is consistent with the law of Tn-2> Tn-3> Tn-4> Tn-1(n=1,2), to verify the rationality of plant model constructed.