The Heat And Moisture Transfer Mechanism Of Earth Building Based On The Organic Rankine Cycle Co-generation System And The Combi-system Characteristics Study

Most residences in vast rural areas of current China are individual buildings.And the poor envelope thermal performance of these rural residences makes the tremendous heat loss.Especially,during the heating season a lot of coal resources are cost for space heating in north China.With the development of building a moderately prosperous society and increase of the peasants' income,people live in rural areas desire for higher degree of building environment comfort.Nowadays,the government and people start to concerning on the contradiction between the energy cost potential and the need of energy conservation for rural residences.In this thesis,a new technical route is presented to solve this contradiction by using earth construction method to improve the rural residence thermal performance and using the Organic Rankine Cycle technology to improve the low grade energy utilization for energy saving.This work was supported by the National Natural Science Foundation of China(Grant No.51678024).Traditional earth building materials are the mainstay of a significant proportion of past societies.Earth buildings have attracted more and more attention for the advantages like energy conservation,recyclable characteristic,low cost and energy consumption for processing,non-pollution,etc.But for well hydrophilic feature,earth buildings are affected by the water from indoor and outdoor environment of air humidity.Water intrusion causes the thermal performance of building envelop change,and then affects the indoor thermal and humidity environment comfort.Recently,although many studies have focused on earth buildings,studies specifically describing the heat and moisture transfer mechanism of earth buildings are scarcity.Summarizing and dissecting the heat and moisture transfer mechanism of earth buildings is needed to develop these sustainable architectural forms and to direct the future practice.In this thesis,the earth building envelope is used as the heat sink for Organic Rankine Cycle co-generation system.Correlative basic problems of the earth building envelope's thermal characteristics and the Organic Rankine Cycle co-generation system's thermal process are studied by theoretical method and experimental method.In comprehensive analysis of the existing theory about heat and mass transfer in porous media,the governing equations of heat and mass transfer in earth building envelope under the temperature gradient and water content gradient have been built,according to corresponding property parameters,transport function and Philip-De Vries heat and mass transfer model of porous media.This model is a transform and simplification form the Philip-De Vries model,which is more brevity and numerical efficiency by generalizing the function with less independent variables.Then an onedimensional rammed earth experiment has been performed to verify this model and the results prove that the model is accurate enough for engineering prediction.Moreover,mass transfer model under steam density gradient at the boundaries for earth building envelope has been built according to Lewis relation.And a continuous moisture absorption experiment of rammed earth has been performed to verify this model at the boundaries for earth building envelope which is proposed to evaluate mass transfer process at boundaries and to establish relationships between earth building envelope and the indoor or outdoor environments.In addition,based on energy and mass conservation a steady state model for Organic Rankine Cycle co-generation system has been built,which includes heat exchanger models using ?-NTU method with considering moving boundary method;an expander model with dividing the expansion process into isentropic and isovolumetric expansion processes,etc.And this model is used for predicting the Organic Rankine Cycle co-generation equipment when the boundary condition changes.At the end,an integrity earth building model including the earth building envelope,indoor and outdoor temperature and humidity conditions has been built.The calculation programs for earth building and Organic Rankine Cycle co-generation equipment,using Fortran basing on TRNSYS environment,has been worked out to get the numerical solutions of the proposed models.Digital simulation experiment results for the earth building and Organic Rankine Cycle combi-system,basing on the former programs in TRNSYS environment,can be used to analysis the heat and moisture transfer mechanism of earth building,the system characteristics of the Organic Rankine Cycle and the interaction between these two parts.Consequently,the study results can be used to support and guidance the earth building practice for improving the earth building indoor environment and to optimize the relative parameters of Organic Rankine Cycle co-generation system.