Analysis of the spatiotemporal temperature fluctuations inside an apple cool store in response to energy use concerns

Abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 0Analysis of the spatiotemporal temperature fluctuations inside an apple cool store in response to energy use concerns Alemayehu Ambaw (a, c) , Niels Bessemans (a) , Willem Gruyters (a) , Sunny George Gwanpua (a) , Ann Schenk (b) , Ans De Roeck (b) , Mulugeta A. Delele (a) , Pieter Verboven (a) , Bart M. Nicolai  It has been demonstrated that fan and refrigeration cycling works to save energy. Load shifting of controlled atmosphere stores for saving energy costs seems worthwhile. AbstractEnergy cost concerns have led to question the temperature and air flow regimes in cool store facilities. In this paper, a CFD model of the air flow and temperature dynamics inside an apple fruit Page 1 of 33 1 cool store was developed, validated and used to analyse energy cost saving alternatives. Load shifting was attempted by cycling the temperature set point between 1.2 °C and 0.6 °C following a day/night regime. Discontinuous use of the cooling operation, including 12 h on / 12 h off; 10 h on / 14 h off; and 8 h on / 16 h off were also investigated. The study showed that the air circulation fan is the major source of heat load. Hence, an attempt to reduce energy cost should first deliberate on reducing the fan operation time. The study developed a generic tool to analyse temperature control options inside an apple cool store in response to energy use concerns.

Artificial fruit for monitoring the thermal history of horticultural produce in the cold chain

“…Monitoring postharvest fruit temperature history of fresh fruits is thus essential to evaluate the efficacy of existing commercial cold-chain unit operations but also to explore new cooling strategies. Typical examples of such recent cooling strategies are flow reversal for forced-air precoolers (Ferrua and Singh, 2009), ambient loading for refrigerated containers (Defraeye et al, 2015b) and intermittent operation of cooling fans in cold storage rooms and refrigerated containers (Ambaw et al, 2016;Lukasse et al, 2011;Thompson, 2004). Fruit temperature measurements are also essential to evaluate and develop new ventilated bulk packaging (Gruyters et al, 2017;O'Sullivan et al, 2016;Wu et al, 2017).…”

A numerical evaluation of adaptive on-off cooling strategies for energy savings during long-term storage of apples

“…The air side heat transfer coefficient of the cooling unit (hc, W m -2 K -1 ) was represented by the Colburn ja factor (Bejan, 1993;Tso et al, 2006). Figure 3 shows the experimental results obtained from Ambaw et al (2016) of the air temperature dynamics of the tubular heat exchanger during the "off" phase of the cooling cycle. Since the initial temperature of Tc was not known a best fit was used, and the inlet air temperature during the "off" phase of the cooling cycle was approximated with an exponential curve which corresponds well with the experimental results and model (1).…”

“…It should be noted that a continuous airflow was used in this study. By allowing the air ventilator fans to stop working, it is possible to reduce the energy consumption as was pointed out by East et al (2013) and Ambaw et al (2016).…”

“…Coolstore managers concluded that small temperature differentials (0.3 to 0.5 °C ) used today in coolstores are optimal for reducing energy consumptions and they are not eager to explore other settings. Aspects such as airflow distribution affected by room and stacking design are considered much more relevant for improving temperature uniformity (Ambaw et al, 2016;Delele et al, 2012Delele et al, , 2009. For industrial relevance purposes of the present study, reference is given to results of an experimental trial of temperature fluctuation measurements in a CA coolstore filled with 126 tons (305 wooden bins) of 'Jonagold' apples (Veiling Haspengouw, Sint-Truiden, Belgium) operated at 0.8 °C with a differential of 0.3 °C (data not shown).…”

“…By using a lumped-model analysis, East et al (2013) showed that avoiding cooling during peak price hours and concentrating cooling during off-peak hours may result in a 40 % cost reduction, but does not save on actual energy use while allowing more temperature fluctuations. By reducing the working time of the fans with an on/off cycling regime, Ambaw et al (2016) found that there was a significant decrease in heat load, showing promising possibilities for energy reduction compared to continuous cooling without compromising the product temperatures. However, the impact of the temperature fluctuations on the quality of the apples was not investigated.…”