Performance evaluation of heat pump dryer

Pal, US; Khan, Mohammad Aktaruzzaman

doi:10.1007/s13197-010-0031-3

Cited by 16 publications

(13 citation statements)

References 7 publications

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“…The drying time of samples decreased from 390 min to 270 min as the air velocity was increased from 1.41 m/s to 3.24 m/s. The results were consistent with the results those obtained by Pal and Khan [22] for heat-sensitive crops.…”

Section: Drying Ratesupporting

confidence: 93%

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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: Drying Ratesupporting

confidence: 93%

“…The coefficient of performance (COP) can be used to evaluate the amount of work converted into heat for two different system operations: cooling and heating. For a heat pump, the heat transfer from the system to the hot body is desired, and the coefficient of performance is expressed as [22],…”

Section: Coefficient Of Performancementioning

confidence: 99%

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 air heating process in the condenser was assumed to be a constant humidity process. The condenser model can be represented by Equations (13) and (14) for the energy balance and mass balance, respectively, in the HPDU modelling system. The humidity of air was also constant in the heating process for the CHPD.…”

Section: Condenser Modelmentioning

confidence: 99%

“…With the widely held application of the HPDs in industry, various HPD technologies have been developed and promoted. The HPDs could be divided into three categories based on the air loops: The open-loop type [5][6][7]; the partially open-loop type [8][9][10]; the closed-loop type [11][12][13]. For the open-loop type heat pump dryers (OHPDs), the drying performance is directly affected by the ambient conditions [14], since the heat source is typically the ambient air.…”

Section: Introductionmentioning

confidence: 99%

“…Liu et al [30] proposed a CHPD and studied the effect of the air temperature and the air flow ratio on the performance of the system. However, due to the inherent characteristics of the closed-loop, the excess heat generated by the compressors in the CHPDs tended to be discharged into the ambient air through external condensers [12,13,31] which reduced the energy efficiency of the closed-loop system. For instance, it has been reported that the heat exhausted from an external condenser accounted for 37.92% and 28.79% of the total thermal energy involved in a CHPD for ginger drying, when using air and nitrogen as the drying media, respectively [31].…”

Section: Introductionmentioning

confidence: 99%

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Performance Analysis of Heat Pump Dryer with Unit-Room in Cold Climate Regions

et al. 2019

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This study presents the development and evaluation of a novel partially open-loop heat pump dryer with a unit-room (HPDU). The unit-room was designed to enable the ambient air to be mixed with the return air, thereby reducing the influence of the ambient air on the system performance, while maintaining a high system thermal efficiency. A modelling system for the HPDU was developed and validated based on a real-scale experimental study. By using the modelling system, the system characteristics under different ambient conditions and bypass factors were analyzed. The energy benefit of the proposed HPDU was quantified through a comparative study with a closed-loop heat pump dryer (CHPD). It is evident that a maximal specific moisture extraction rate (SMER) and a minimal total energy consumption (TEC) existed when changing the bypass factor of the HPDU under certain ambient temperatures. Compared to the CHPD, the coefficient of performance (COP) of the HPDU increased by up to 39.56%, presenting a significant energy benefit for the application of HPDU.

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Heat Pump Assisted Drying Technology – Overview with Focus on Energy, Environment and Product Quality

Jangam

Mujumdar

2011

Modern Drying Technology

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Performance evaluation of heat pump dryer

Cited by 16 publications

References 7 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

Performance Analysis of Heat Pump Dryer with Unit-Room in Cold Climate Regions

Heat Pump Assisted Drying Technology – Overview with Focus on Energy, Environment and Product Quality

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