Modelica-based modelling of heat pump-assisted apple drying for varied drying temperatures and bypass ratios

Jokiel, Michael; Bantle, Michael; Köpp, Christian; Verpe, Espen Halvorsen

doi:10.1016/j.tsep.2020.100575

Cited by 17 publications

(9 citation statements)

References 13 publications

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“…The heat pump system consists of a compressor, evaporator, condenser, and expansion valve, etc. The refrigerant, such as R134a, R410, R717, or R744 [9], is evaporated into gas in the evaporator, driven by a compressor, which absorbs a large amount of heat energy from the air. The gaseous refrigerant is compressed into a high-temperature, high-pressure gas, which then enters the condenser to release heat to the drying medium (air), repeating the cycle until the material is dried.…”

Section: Introductionmentioning

confidence: 99%

“…Their results provided important information about the moisture migration and the required energy during the process. A heat pump-assisted drying process can reduce the energy demand by 84% compared to traditional drying using fossil fuels, but possibly results in up to a 69% longer drying time due to the higher humidity [9]. To produce consistent-quality seaweed and shorten the drying time, Sarbatly et al [8] studied the heat pump drying kinetic and thermodynamic properties of Eucheuma spinosum, and found that the difference in algae enthalpy values used in each experiment was up to 1.74 times, but the reason was not explained.…”

Section: Introductionmentioning

confidence: 99%

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Heat Pump Drying of Kelp (Laminaria japonica): Drying Kinetics and Thermodynamic Properties

Zhang

et al. 2022

Processes

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The main objective of this research is the study of the drying kinetics and thermodynamic properties of kelp using heat pump drying technology. The effects of the independent variables of temperature (20–50 °C), air velocity (0.3–1.3 m/s), humidity (20–50%), and thickness (0.8–4.2 mm) on the drying time, moisture uniformity, effective moisture diffusivity (Deff), activation energy (Ea), enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) were investigated. The results show that the Page model was effective in describing the moisture content change of kelp during heat pump drying. The Deff varied from 1.00 × 10−11 to 13.00 × 10−11 m2/s and the temperature, air velocity, humidity, and thickness had significant effects on drying time and moisture uniformity. Higher temperature and air velocity with proper humidity shortened the drying time and lessened the influence of thickness on moisture uniformity. The Ea (16.38–26.66 kJ/mol) and ΔH (13.69–24.22 kJ/mol) were significantly increased by thickness. When the temperature was 40 °C, air velocity 1.3 m/s, and air humidity 40%, the moisture content was reduced to 18% in 5 h, with a homogeneous moisture content. This study clarifies the regularity of moisture change inside kelp and provides a theoretical reference for the development of macroalgae drying technology.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat Pump Drying of Kelp (Laminaria japonica): Drying Kinetics and Thermodynamic Properties

Zhang

et al. 2022

Processes

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“…Nevertheless, the cycle of the traditional convection drying method using box-type dryers is either an open, semiopen, or closed rigid drying cycle, which cannot effectively utilize the constantly changing fresh or return air [16]. Either cycle with bypass rate can be mixed at a certain proportion of return air to achieve energy-saving drying [17]; however, it does not meet the low dew point dehumidification requirements of desiccant wheel dehumidification. In this paper, the dehumidification characteristics of heat pump drying are analyzed.…”

Section: Introductionmentioning

confidence: 99%

Research on Energy-Saving Experimental of Critical Dehumidification of Combined Drying by Dehumidification Wheel and Heat Pump

Wang

Song

Jin

et al. 2021

Journal of Food Quality

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In order to further decrease the energy consumption of desiccant wheel dehumidification, the drying medium circulation characteristics of a system combining heat pump drying with desiccant wheel dehumidification were investigated. Moreover, the critical dehumidification conversion mechanism was studied. The analysis of the heat pump hot air circulation system demonstrated that the heat pump system has the best dehumidification efficiency. Through the analysis of the system combining heat pump drying with desiccant wheel dehumidification, the critical conversion point was determined. The critical dehumidification mechanism was further verified using an online temperature and humidity measurement system. To investigate the effect of the critical point on energy consumption and drying quality and develop a drying model, response surface experiments were performed based on the effects of regeneration temperature, drying temperature, and conversion point relative humidity on rehydration, color difference, and specific moisture extraction rate (SMER). The optimal conversion point humidity was determined to be about 46% RH, which was slightly different from the test optimization value of 45.6% RH. In addition, comprehensive optimization and experimental verification of the influencing factors were conducted. The results demonstrated that the R2 values of the three models were greater than 0.98, and the experimental factors had a significant effect on drying quality and energy consumption. When the regeneration temperature was 96°C, the drying temperature was 53°C, the relative humidity of the conversion point was 46%, the color difference was 46.3, the rehydration ratio was 5.75, and the SMER was 1.62 kg/kW·h.

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“…In the study [11], jujube slices dried by HPD presented a significantly lower color difference (ΔE) and shrinkage ratio than hot air drying. The authors of [12] studied the use of a heat pump with CO 2 as a working medium to provide heating and cooling in the drying cabinet for typical food drying temperatures of 50-70 °C and for various ratios of moist air being bypassed. In [13], banana slices were dried at different temperatures (37, 40 and 43 °C) in a closed-loop heat pump drying system.…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

The influence of different drying methods on the quality attributes of beetroots

Liu

Sabadash

Duan

et al. 2022

EEJET

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Beetroot is recognized as a health-promoting vegetable due to its abundant source of bioactive compounds. Drying methods significantly influence the quality of products. Therefore, it is important to choose a suitable drying method to obtain high quality of dried beetroots. The aim of this research was to investigate the influence of different drying methods on the quality attributes of beetroots. Fresh beetroots were dehydrated by freeze drying (FD), heat pump drying (HPD), vacuum drying (VD), microwave drying (MD) and microwave vacuum drying (MVD), respectively. The drying time, final moisture content, rehydration ratio, color, microstructure, betalain content and total flavonoids content of beetroots prepared by different drying methods were analyzed. The results showed that MVD and MD were superior to VD, HPD and FD in terms of drying time. The drying time (0.77±0.03 h) of MD was reduced by 97.40 % compared with FD, which was only 9.83 % of VD and 11.27 % of HPD. No significant differences in the final moisture content among beetroots dried using different drying methods were observed. Beetroots dried by FD showed the most desirable color and porous structure. Besides, beetroots dried by MVD exhibited the largest rehydration ratio, while the lowest rehydration ratio appeared in the beetroots obtained using MD. In addition, beetroots prepared by HPD illustrated the highest contents of betacyanin, betaxanthin and total flavonoids, which were 5.48±0.03 mg/g, 2.40±0.02 mg/g and 24.71±0.47 mg rutin equivalent/g, respectively. These results identify that it is difficult to achieve the best quality dried beetroots using a single drying method. Therefore, considering the quality attributes, the combined drying method (HPD+MVD) would be a very promising alternative method for obtaining dehydrated beetroots

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Modelica-based modelling of heat pump-assisted apple drying for varied drying temperatures and bypass ratios

Cited by 17 publications

References 13 publications

Heat Pump Drying of Kelp (Laminaria japonica): Drying Kinetics and Thermodynamic Properties

Heat Pump Drying of Kelp (Laminaria japonica): Drying Kinetics and Thermodynamic Properties

Research on Energy-Saving Experimental of Critical Dehumidification of Combined Drying by Dehumidification Wheel and Heat Pump

The influence of different drying methods on the quality attributes of beetroots

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