Mathematical Model for a Heat Pump Dryer for Aromatic Plant

Hossain, M. A.; Gottschalk, Klaus; Hassan, Mohammad Shoeb

doi:10.1016/j.proeng.2013.03.154

Cited by 34 publications

(24 citation statements)

References 6 publications

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“…Usually, higher airflow velocity intensified drying rate change by the drying time. This result was in line with many earlier research findings on leaf drying [2], [4], [9], [13] and [16].…”

Section: Effect Of Air Velocitysupporting

confidence: 93%

“…Their findings were in line with those of Rayaguru and Routray [12]. Hossain et al [13] found that low relative humidity (20 %) played an important role in reducing the moisture content of herbs (89 %wb) (wet basis) to safe final levels (9 %wb). Fatouh et al [14] observed that drying air temperature and air velocity had a significant effect on the drying rate.…”

Section: Introductionsupporting

confidence: 79%

“…Here, an increase in COP was observed for the moderate velocity of air, which was because of the increase in the temperature difference between temperatures at condenser and evaporator as a result of the decrease in velocity of air to the evaporator. Coefficients of performance below 4 are normally not acceptable for drying applications [13] and [27].…”

Section: Dryer Performancementioning

confidence: 99%

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Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Babu¹,

Kumaresan

Raj³

et al. 2020

SV-JME

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The design of a batch drying chamber with multiple trays for the thin-layer drying of fragile, heat-sensitive food materials, such as edible leaves, is a challenging task. It is essential to ensure good air distribution with minimum pressure drop in all the compartments of the drying chamber to obtain uniform drying of the product. In the present work, a drying chamber that was optimized from different configurations using computational fluid dynamics (CFD) software was fabricated and tested in the heat pump dryer. The experimental investigation was carried out with an optimized configuration for the temperature range of 50 ºC to 60 ºC, the relative humidity range of 20 % to 12 %, and air velocities of 1.41 m/s, 2.39 m/s, and 3.24 m/s. These optimal operating conditions were chosen based on an extensive literature survey on leaf drying. It was found that the drying process took place only in the falling rate period, fully controlled by the mechanism of liquid diffusion. The effects of air velocity on the performance parameters of the dryer were studied. Calculations based on the mean average parameters of the experimental data showed that a relatively higher heat utilization factor (0.17), moisture extraction ratio (0.375 kg/h), specific moisture extraction ratio (0.1529 kg/(kWh)), coefficient of performance (4.60), drying efficiency (76.23 %) and lower specific energy consumption (1.16 kW/kg) were obtained for a moderate drying velocity of 2.39 m/s in the heat pump drying process due to higher convection mass and heat transfer effects. Drying curves were plotted for different drying conditions and discussed. The findings were in agreement with those of many earlier research studies listed in the references section. The tested drying chamber can be used for drying all kinds of leaves in a heat pump dryer. Keywords: Amaranth leaves, batch dryer, heat pump dryer, coefficient of performance, thin-layer drying Highlights • A drying chamber optimized from different configurations using computational fluid dynamics (CFD) software is fabricated and tested in a heat pump dryer for drying Amaranth leaves. • Good air distribution with minimum pressure drop is ensured in all the compartments of the newly designed drying chamber to obtain uniform drying of the product. • The drying process of batches of spread-out material takes place only in the falling rate period. • Better results are obtained for a moderate drying velocity of 2.39 m/s in the heat pump drying process. • Air velocity, relative humidity, and the drying temperature are found to influence the rate of drying mutually. • The newly designed drying chamber is suitable for drying all kinds of leaves in a heat pump dryer.

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Section: Effect Of Air Velocitysupporting

confidence: 93%

Section: Introductionsupporting

confidence: 79%

Section: Dryer Performancementioning

confidence: 99%

See 1 more Smart Citation

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Babu¹,

Kumaresan

Raj³

et al. 2020

SV-JME

View full text Add to dashboard Cite

show abstract

“…Heat pump (HP) drying can improve energy efficiency and independently control the drying temperature and air humidity (Minea, 2013;Yang et al, 2013;Zielinska et al, 2013;Artnaseaw et al, 2010), which is especially suitable for temperature sensitive vegetables and fruits as drying can occur at low temperature (Fan et al, 2014;Hossain et al, 2013;Hii et al, 2012). However, heat pump drying is a rather slow drying process.…”

Section: Introductionmentioning

confidence: 99%

Drying characteristics of Chinese Yam ( Dioscorea opposita Thunb .) by far-infrared radiation and heat pump

Song

Zhang

2018

Journal of the Saudi Society of Agricultural Sciences

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Chinese Yam chips were dried using a heat pump (HP) dryer alone or in combination with far infrared radiation (FIR) at 500, 1000 and 2000 W (500 FIR, 1000 FIR, and 2000. The experimental results were presented in terms of the drying characteristics, and dried product qualities (shrinkage, color, texture, percentage of rehydration, and moisture content). Samples with initial moisture content of approximately 76% (w.b.) were dried to a final moisture content of <17% (w.b.) at the drying temperature of 50°C and at an air flow rate of 1.0 m s À1 for all of the experiments. The data showed that FIR + HP drying increased the drying rate by reducing the drying time, and the resulted dried Chinese Yam chips generally had higher values of lightness and comparable values of redness and yellowness than the HP-treated samples. In the case of HP + 1000FIR, the dried Chinese Yam chips had lower shrinkage, improved rehydration ability, lower hardness and higher brittleness than those dried by HP, HP + 500FIR and HP + 2000FIR. It is worth noting that the total energy used for FIR-assisted drying processes decreased with the increase of FIR intensity. The present data suggest that HP + FIR drying is an effective and economical method for Chinese Yam chip drying, and HP + 1000FIR can obtain the best dried product. Ó 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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“…Heat pump (HP) drying can improve energy efficiency and independently control the drying temperature and air humidity [9,10,11,12] which is especially suitable for temperature sensitive vegetables and fruits as drying can occur at low temperature [13,14,15]. However, heat pump drying is a rather slow drying process.…”

Section: Introductionmentioning

confidence: 99%

Study of Iron Yam-Chip (Dioscorea opposita Thunb. cv. Tiegun) Dehydration Using Far-Infrared Radiation Assisted Heat Pump Drying

Song

Luming²

2014

JFNR

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Iron Yam chips were dried using a heat pump (HP) dryer alone or in combination with far infrared radiation (FIR) at 500, 1500 and 3000 W (500 FIR, 1500 FIR, and 3000 FIR, respectively). The experimental results were presented in terms of the drying characteristics, and dried product qualities (shrinkage, color, texture, percentage of rehydration, and moisture content). Samples with initial moisture content of approximately 76% (w.b.) were dried to a final moisture content of < 17% (w.b.) at the drying temperature of 50°C and at an air flow rate of 1.0 m s-1 for all of the experiments. The data showed that FIR+HP drying increased the drying rate by reducing the drying time, and the resulted dried Iron Yam chips generally had higher values of lightness and comparable values of redness and yellowness than the HP-treated samples. In the case of HP+1500FIR, the dried Iron Yam chips had lower shrinkage, improved rehydration ability, lower hardness and higher brittleness than those dried by HP, HP+500FIR and HP+3000FIR. It is worth noting that the total energy used for FIR-assisted drying processes decreased with the increase of FIR intensity. The present data suggest that HP+FIR drying is an effective and economical method for Iron Yam chip drying, and HP+1500FIR can obtain the best dried product.

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Mathematical Model for a Heat Pump Dryer for Aromatic Plant

Cited by 34 publications

References 6 publications

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Drying characteristics of Chinese Yam ( Dioscorea opposita Thunb .) by far-infrared radiation and heat pump

Study of Iron Yam-Chip (<i>D</i><i>ioscorea</i><i> opposita </i>Thunb. cv. Tiegun) Dehydration Using Far-Infrared Radiation Assisted Heat Pump Drying

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