ANALISIS KINERJA KOMPOR BRIKET DITINJAU DARI VARIASI UDARA MASUK DAN JUMLAH LUBANG PADA RUANG BAKAR

Briket merupakan salah satu alternatif bahan bakar yang berasal dari batu bara, serbuk kayu gergaji, dan tandan kelapa sawit yang bisa dijadikan bahan bakar padat. Kompor briket adalah alat pemanfaatan yang dikhususkan untuk beberapa briket sebagai alat bakar skala rumah tangga. Kompor briket juga menjadi salah satu solusi terbaik dalam meningkatkan sistem pembakaran briket selama ini yang masih kurang diminati dan perlakuannya masih tradisional. Pada rancangan kompor biobriket digunakan penambahan fan untuk meingkatkan efisiensi dari alat itu sendiri. Kinerja dari kompor biobriket sangat dipengaruhi oleh aliran udara yang masuk sebagai penunjang proses pembakaran. Tujuan utama penelitian ini adalah untuk mendapatkan desain kompor biobriket terbaik melalui uji eksperimental prototype kompor biobriket dengan memvariasikan kecepatan udara masuk yaitu tanpa fan (natural draft), 6 m/s, dan 8,3 m/s dan setiap variasi kecepatan tersebut memvariasikan jumlah lubang dari ruang bakar kompor biobriket itu sendiri yakni 71, 63, dan 55. Efisiensi kompor briket menggunakan briket arang tempurung kelapa berkisar 10,14% - 24,10% dimana yang terkecil berasal dari natural draft lubang 55 dan yang terbesar berasal dari kecepatan fan 8,3 m/s dengan lubang sebanyak 63. Untuk lubang 71 pada kecepatan fan 8,3 m/s memiliki nilai terbaik dengan start-up time selama 44 detik dan boiling time selama 300 detik. Untuk FCR terendah didapatkan pada natural draft dengan lubang 55 yaitu sebesar 1,312 kg/jam karena udara masuk memengaruhi jumlah bahan bakar yang terbakar.

Heat Exchange in Staggered Threaded Pipe Banks with Similar Developed Surface Patterns under Natural Draft Conditions

Helical pipes with similar developed surface patterns efficiently operate under forced convection conditions. The available literature describes their essential advantages over the tubes of a round-ribbed profile and the possibility of their application as a heat-exchanging section for the air-cooling unit. However, the peculiarities of the operation of such units require checking an opportunity for the use of helical pipes with similar developed surface patterns under natural draft conditions. The purpose of the research is to get new data on the flow structure in the intertube space of the staggered banks of such pipes under natural draft conditions. These data are required for the in-depth analysis of the appropriateness of the use of such pipes for “dry” air cooling systems. The methods of investigation included the use of the academic licensed software package ANSYS Student for numerical computations. It was established that the heat exchange in ribbed pipes under natural draft conditions is specified first of all by the parameters of the staggered bank (longitudinal and transversal pitches of the arrangement of pipes in the bank) and the geometric parameters of the pipes, in particular the pitch between the humps and the dents on the tube surface that form its helical surface. Design ratios were suggested for the determination of the averaged heat exchange in the staggered banks of the single-thread helical pipes with similar developed surface patterns. It was shown that the pitch characteristics of the banks have the greatest effect on the similarity equation. A preliminary validation was carried out for the methods adopted for the design of helical pipes and the known methods used for the computation of the staggered banks of smooth cylindrical pipes. The obtained research data can be used for the evaluation of the intensification of the heat exchange and for the flow analysis in order to increase the efficiency of the heat-exchange equipment.

Influence of Operation Schemes on the Performance of the Natural Draft Hybrid Cooling System for Thermal Power Generation

For thermal power generation, the natural draft hybrid cooling system (NDHCs) with airflows in parallel design gives a multi-objective solution for water saving, performance enhancement and maintenance issues, like corrosion, by switching the loads of wet and dry sections. Performances of dry and wet sections interact with each other in the highly integrated system, increasing the complexity of operation strategies. In this context the present paper examines eight different operation schemes to reveal the relationships of ambient conditions and operation schemes. Comprehensive comparisons in the view of cooling efficiency with a same water inlet temperature are conducted firstly. Results show that there exists energy-saving potentials of the water evaporated rate, cooling performances and the pump power for different schemes. Based on the practical boundary conditions, including those of weather data, operation hours and market factors, optimal operation strategies of hybrid cooling are designed to minimize the operation costs of the energy system. For the 660 MW power generating unit integrated with a natural draft dry cooling system (NDDCs), operation costs based on NDHC after optimization decreased about 0.8% in 2010 and 0.35% in 2018 compared with that of the basic system. When comparing with the designed operation modes of hybrid cooling, 0.07 million dollars is saved after optimization.