학술논문
1 kW급 스털링엔진 고온 열교환기 시스템 모형화 / System Modeling of High Temperature Heat Exchanger for 1 kW Class Stirling Engine
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
최근들어 계절별 에너지원의 수급조절, 발전소 건설 입지악화 및 가스저장시설 확충문제 해결을 위한 분산형 발전설비의 보급 확대가 필요하고, 기후변화협약, CO2 배출권 거래제 등 국제환경규제가 경제 문제로 대두되고 있어 새로운 온실가스 감축수단이 필요할 뿐만 아니라 에너지의 효율적 이용 및 고효율 에너지 시스템의 보급을 위해 초소형 열병합 발전 시스템의 확대는 필연적이다. Micro CHP (Combined Heat and Power) 는 1 kW에서 10 kW의 전기에너지를 생산하면서 발생되는 폐열을 회수한다. 그 종류로는 연료전지, 내연기관, Micro 가스터빈, 스털링엔진 등이 있다. 사용 목적과 크기로 볼 때, 가정용으로는 스털링엔진이 가장 적합하다. 본 연구에서는 스털링엔진의 성능 및 효율 향상의 주요 기기인 고온 열교환기 설계를 위해 열전달 현상 분석하였다. 개발하고자 하는 1 kW 스털링엔진은 Micro-CHP에 속하여 가정용으로 소형화하기 위해 고온 열교환기와 연소기가 매우 가깝게 위치하고 있다. 이 때문에 연소기와 고온 열교환기 사이에 대류 열전달뿐만 아니라 복사 열전달도 중요한 역할을 하고 있다. 이러한 이유로 수치해석을 이용하여 형상 개선과 축열 조건 유무에 따른 열전달 현상을 검토함으로써 연소실 내 좁은 공간에서 고온의 온도차로 발생하는 복사열전달의 영향을 확인할 수 있었으며, 해석 결과를 이용하여 형상 개선 방안을 제시하였다. 또한 간단한 사이클 해석을 통하여 초기 모델과 형상을 개선된 모델 사이에서의 수치해석 결과를 타당하게 비교하였다.
The availability of the thermal energy has been deeply recognized recently to encourage the cascade usage of thermal energy from combustion. Within the framework, a 1 kW class stirling engine based cogeneration system has been proposed for a unit of a distributed energy system. Numerical analysis is conducted to design the high temperature heat exchanger of Stirling engine by using the commercial CFD solver, FLUENT. The fin-tube type of heat exchanger is designed, considering the type of engine which is beta-configuration. Design parameters of fin are width, length, thickness and shape. The optimal design of heat exchanger considering the heat transfer capability is suggested by using the calculation results.The capacity has been designed to be adequate for the domestic usage, which requires high compactness, therefore high temperature heat exchanger was closed to combustion chamber. For that reason, convection and radiation heat transfer are important factor. To improve efficiency, heat transfer phenomenon of important part was analyzed about heat recuperation in combustion. The result show design direction of combustion chamber. In addition, the original model is compared with the optimal prototype at the same boundary condition. However optimal model should have higher temperature of isothermal condition than the original one at cylinder head. Cycle adjustment is conducted to find proper temperature of optimal model and to have plausible numerical results.
The availability of the thermal energy has been deeply recognized recently to encourage the cascade usage of thermal energy from combustion. Within the framework, a 1 kW class stirling engine based cogeneration system has been proposed for a unit of a distributed energy system. Numerical analysis is conducted to design the high temperature heat exchanger of Stirling engine by using the commercial CFD solver, FLUENT. The fin-tube type of heat exchanger is designed, considering the type of engine which is beta-configuration. Design parameters of fin are width, length, thickness and shape. The optimal design of heat exchanger considering the heat transfer capability is suggested by using the calculation results.The capacity has been designed to be adequate for the domestic usage, which requires high compactness, therefore high temperature heat exchanger was closed to combustion chamber. For that reason, convection and radiation heat transfer are important factor. To improve efficiency, heat transfer phenomenon of important part was analyzed about heat recuperation in combustion. The result show design direction of combustion chamber. In addition, the original model is compared with the optimal prototype at the same boundary condition. However optimal model should have higher temperature of isothermal condition than the original one at cylinder head. Cycle adjustment is conducted to find proper temperature of optimal model and to have plausible numerical results.