HEATING INSIDE A GREENHOUSE AT NIGHT USING SOLAR ENERGY

ABSTRACT The outdoor air temperature is not constant especially in spring in Columbus, Ohio (U.S.A). The average night temperature ranges from -2 to 20 o C which is too low for the germination of most seeds. A good knowledge of the future outdoor air temperature is necessary to decide if greenhouse heating is needed for the next day. Using measured temperatures from the preceding days and considering the minimum and maximum temperatures given by the weather forecast, it was possible to accurately compute the temperature for the next day. Green pepper seeds were used in this study. A solar system was used to heat the air inside a greenhouse at night using an air-water-air heat exchanger and make a comparison with an unheated greenhouse. The performance of the solar collector and methods of heat exchange were tested. It was shown that the solar energy collected was sufficient for warming a nursery greenhouse overnight. The system operated with a hot water flow rate of 0.52 L/min and an air flow rate of 8.53 m 3 /min and could maintain the greenhouse temperature between 16 and 20 o C. The quantity of heat collected and delivered by the solar system from incident solar radiation was about 50% in a day. Heating the air inside the greenhouse at night produced 100% germination for all seedlings. In comparison, in the unheated greenhouse the germination ratio was 80% and germination ratio outside the greenhouses was 60%

Mechanical collision simulation of potato tubers

This paper presents the results of an investigation on internal stress progression and the explicit dynamics simulation of the bruising behavior of potato tubers under dynamic mechanical collision. Physical measurements, mechanical tests, advanced solid modeling, and engineering simulation techniques were utilized in the study. The tuber samples used in the simulation were reverse engineered and finite element analysis (FEA) was set up to simulate the collision-based bruising behavior of the potato tubers. The total number of identical tuber models used in the simulation was 17. The numerical data of the FEA results revealed useful stress distribution and mechanical behavior visuals. These results are presented in a frame that can be used to describe bruise susceptibility value on potato-like agricultural crops. The modulus of elasticity was calculated from compression test data as 3.12 MPa. Structural stresses of 1.40 and 3.13 MPa on the impacting (hitting) and impacted (hit) tubers (respectively) were obtained. These stress values indicate that bruising is likely to occur on the tubers. This research paper provides a useful how-to-do strategy to further research on complicated bruising investigations of solid-like agricultural products through advanced engineering simulation techniques. Practical applications: This research aims to simulate realistic dynamic deformation of potato tubers during mechanical collision, which is very hard to achieve through physical or analytical expressions. This is attractive because related food processing industries have shown their interest in determining the physical properties and bruising behavior of food/agricultural products using experimental, numerical, and engineering simulation methods so that it can be used in their food processing technology. Very limited data have been found available in the literature about the subject of FEM-based explicit dynamics simulation of solid-like agricultural crops such as the self-collision case of potato tubers (which is very important for indoor or outdoor potato processing). Comparative investigations on determination of modulus of elasticity are very limited as well. Most of the research focused on single calculation theory and linear static loading assumption-based FEM simulation solutions. Here, we report a “how-to-do” case study for dynamic self-collision simulation of potato tubers