An Investigation of Practical Process Design and Control of a Soil Warming System with Heat Generated in Compost

摘要

An optimum design and a control method of a soil warming system with heat generated in compost were investigated, following a concept of process design. Provided that many of the input data such as thermal physical properties of compost bed, the amount of heat required to soil warming, and the micrometeorological condition in a greenhouse are given and that the dimensions of the tube for heat extraction is premised, there are only two decision variables to be optimized. One is the space of arrangement of the tubes for heat extraction and the other is the flow rate of medium fluid in the tubes. Optimum numerical values of the decision variables were obtained, taking account of stability in operation, increase in heat efficiency and reduction of the cost of equipments of heat source. Assuming that the system is applied to the protected cultivation in a small scale, a representative example of the flow sheet of the system was proposed, and operation manuals of the system were described. Optimum numerical values of the decision variables, operation manuals and the flow sheet proposed here would become the basis of the detailed design of equipments and devices of the system. 堆肥発酵熱を利用した土壌加温システムの最適設計・制御の方法を, プロセス設計の概念に基づいて検討した。混合素材の熱的物性値, 土壌加温に必要な熱量, 温室内微気象条件などが前提条件として与えられ, 熱抽出管の規格が決められているとき, 最適化によって決定すべき決定変数は, 熱抽出管の配管間隔と熱抽出管内の通水量の二つで, 操作の安定性, 熱効率の向上, 熱源装置の設備費軽減の観点からそれらの最適値が求められた。更に, 本システムを小規模施設へ適用することを前提に, 土壌加温トータルシステムのフローシートの一例を示し, 操作要領を記述した。ここで得られた決定変数の数値, 操作要領, フローシートは機器設備の詳細設計を行う際の基礎となるだろう。