# Bulk Grain Cargo Hold Condensation Based on Computational Fluid Dynamics
## 1 Introduction  
In recent years, the issue of cargo grain deterioration has received wide attention. Over the past five decades, the grain trade throughout the world has expanded rapidly [1], but almost one-third of the food produced worldwide is lost due to spoilage or waste [2]. According to the classification of the world's major grain trade, soybean accounts for more than 20% [3]. The soybean trade throughout the world is 340.91 million tons in 2020, followed by 324.57 million tons in 2021 and 333.57 million tons in 2022, as shown in Figure 1. From the perspective of transportation mode, shipping is the main means via which the soybean is traded globally. Normally, a single ship can carry approximately 80,000-100,000 tons of soybeans. Once a cargo damage accident occurs, the loss may range from millions to billions (see Table 1). The storage of bulk grain in a cargo hold of a moving ship, which is very different from the storage of bulk grain on land, is frequently influenced by changing solar radiation and sea temperature. Soybeans are a type of grain sensitive to ambient environmental circumstances [4; 5], so when the external temperature decreases, there is a temperature difference between the inside and outside of the grain. The moisture migration, which is caused by temperature gradients, will lead to the creation of high-humidity zones [6] in the hold. The increase in moisture content causes the decomposition of internal substances in soybeans and leads to heat and mold in the grain pile [7; 8; 9]. In the process of maritime navigation, the causes of cargo damage accidents include self-heating, mildew, pollution, condensation, wet damage, pests, etc. [10]. Among these factors, condensation is an important factor causing cargo damage. The condensation in a bulk grain hold refers tothe process of water vapor accumulation after the air among the grain particles reaches a saturation state due to a decrease in temperature, as shown in Figure 2. The objective of this paper is to investigate why condensation is produced on the shipside of a cargo hold. The problem of the deterioration of bulk grain caused by condensation comes first from the grain storage industry on land. In 1987, [PERSON] [11] developed a two dimensional transient model to describe the water transport process due to natural convection within the grain pile, but the model neglected diffusion induced water transport. After this, [PERSON] et al. [12] experimentally explored moisture distribution in the space \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Date** & **Ship Name** & **Voyage** & **Damaged Tonnages** \\ \hline (1) & November 1997 & MV RAM DAS & India to China & 4927 \\ (2) & May 1999 & MV Panamax Star & Brazil to China & 7001 \\ (3) & April 2004 & MV Bunga Saga & Brazil to China & 11,635 \\ (4) & May 2004 & MV Hanjin Tacoma & Brazil to China & 14,031 \\ (5) & September 2012 & MV Tai Prize & Brazil to China & 4991 \\ (6) & July 2014 & MV Grandamanda & Ukraine to & 20,121 \\ (7) & June 2017 & MV Yasa Eagle & Brazil to China & 2598 \\ (8) & August 2017 & MV ADELANTE & Brazil to China & 64,848 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Statistics of damaged bulk grain in tonnage. Figure 1: World grain trade during the period from 2016 to 2022[PERSON]  
Figure 2: Cargo condensation at the stow peripheries. during condensation, and supposed that the vapor distribution is primarily affected by air movement. [PERSON] et al. [13] simulated moisture variations at various locations in 1996 by combining the temperature with the EMC model[PERSON] In 1998, [PERSON] et al. [14] performed simulations to calculate the effect of thermal buoyancy on air motion. Nine years later, [PERSON] et al. [15] conducted an experimental study of moisture movement and the condensation of grains with high relative moisture content and deterioration. [PERSON] et al. [16] conducted numerical simulations of moisture heat transfer in grains with volumetric heat production and the influence of latent heat in 2011.