Performance Evaluation of a Refrigeration System for Fresh Maize Storage

Aims: In this research project, a refrigeration system that will preserve the quality of fresh maize was developed. Study Design: Design of refrigeration system. Place and Duration of Study: Department of Industrial and Production Engineering, Federal University of Technology, Akure, Ondo State, Nigeria, between August 2017 and February 2018. Methodology: The designed system consists of a cooling cabinet, compressor, condenser and an evaporator. The cabinet was designed to store up to 15 kg of maize and a compressor of 1/6 hp was used. The equivalent condenser and evaporator were selected with an equivalent expansion valve. R134a was used as the refrigerant. The cabinet walls were fabricated from mild steel (outside wall), stainless steel (inner wall) and glass wool (insulator). Results: The fabricated system stores fresh maize above its freezing temperature of -1ºC. The system operating temperature ranges from -4 to 2.5ºC with a relative humidity of 90 to 95% for eight hours. Conclusion: The fresh maize was stored for ten days without noticeable changes in the physical appearance and taste of the maize.

Twin Gating System Design for Typical Thin Wall Stainless Steel Castings Based on Fast Pouring Mechanism

The thin wall stainless steel castings is difference to ordinary steel castings in foundry technology. This paper discussed the problems of thin wall stainless steel castings which appearing in the flow controlling board for warm-air pipe, and put forward the foundry technology of this stainless steel castings based on the principle of directional solidification and fast pouring mechanism. According to the theory, twin gating system has been designed for the controlling board castings, and two ladles are pouring into the open twin gating system at the same time. The shrinkage of finally congealing part was fed by two risers. The practice has shown that the design is feasible, there is not cold shut, misrun, scab, and oxidizing for the castings, and the requirements of mechanical properties can be met.

Cracking in Welds of Heavy-Wall Stainless Steel and Nickel Alloy Piping During Fabrication

Heavy-wall austenitic stainless steel and nickel alloy piping components can sometimes suffer cracking during fabrication. Cracking occurs in the materials during fabrication as a result of solidification cracking during welding and reheat cracking (also referred to as stress relaxation cracking or stress relief cracking) during postweld heat treatment (PWHT) such as solution heat treatment or stabilizing heat treatment. This paper describes several case studies of recent cracking in welds of heavy-wall piping components fabricated from Type 321 stainless steel and Alloy 800HT that have occurred during fabrication. The severe cracking occurred in weld metal in each of the heavy-wall components. As a result of investigations, it was concluded that most likely cause for the cracking was a result of reheat cracking occurring during PWHT.