Design Of A Gas Burner-Fan Combination Duct System For An Agricultural Dryer And Simulation Of The Performance Of The Dryer / Anis Syufina Binti Haji Mohammad Saufi.

A thesis submitted to Universiti Teknologi Brunei (UTB) in partial fulfillment of the requirements for the degree of Master of Science (MSc) in Mechanical Engineering.

ABSTRACT
The development towards methods of drying grain crops have been continuously researched.
In this study, the design of a gas-burner fan combination duct system for an agricultural dryer as well as the simulation regarding the performance of the dryer was conducted. The gas-burner fan combination duct system shows a promising endeavor as it is done using liquefied petroleum gas (LPG) which is normally used for cooking purposes, which is easily available.
Thus, the aim of the research is to reach the targeted temperature range of 40 - 60 °C and assess the dryer performance.
The results are focused on the drying performance based on parameters such as drying air temperature, air flowrate, fan performance curve, depth of grain bed, moisture content, and energy content of drying air. The gas-burner fan combination duct system goes through a series of processes to justify the design dimensions, preliminary testing, and material selection through creating a prototype. The fabrication process is commenced which consist of cutting, bending, welding, and assembling process. The experiment is done with measuring the drying air temperature and air velocity using a pocket wind meter.
The study resulted in a decrease in drying air temperature as the air flowrate increases with the highest drying temperature reached to be 74.6 °C at an air flowrate of 0.05189 m3/s. When the duct is covered (limited space for the drying air to pass through), the fan speed as well as the air flowrate increases, resulting in further decrease in drying air temperature. The fan performance curve shows a decreasing depth with increasing air flowrate. For each depth, the air flowrate has a directly proportional relationship with the pressure loss, recording a pressure loss of 680.52 Pa at an air flowrate of 0.1315 m3/s for 90cm depth.
The operating points for the air flowrates were recorded based on the intersection between the static pressure curve and the depths of the grain bed. Using the power regression equation of T = 94.789e -4.832x, the drying air temperature is calculated which obtained a similar relationship between the drying air temperature and air flowrate, obtaining temperatures ranging from 58.2 - 68.6 °C for increasing depths. With increasing depths, the energy received by the drying air decreases, the highest energy recorded is 12.49 MJ/hr at 20cm depth. The effect of grain bed depth on the final weight of grains was evaluated whereas the depth increases, the weight of grains needed to reduce the water content from 28% to 12% also increases.
For further research, a higher air flowrate should be used in order to obtain a lower drying temperature. In addition, different usage of material in terms of burner housing and duct system should be evaluated as well as altering the dimensions of duct system or selecting a different stove burner or fan to be compared with the current research.

Thesis (Degree) - Universiti Teknologi Brunei, 2022