scholarly journals Study on the general dynamic model of biomass drying processes

2018 ◽  
Author(s):  
Le Wang ◽  
Xu Li ◽  
Qiaoling Li ◽  
Duanfeng Lu ◽  
Bin Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Moisture Content ◽  
Dynamic Model ◽  
Equilibrium Moisture Content ◽  
Air Temperature ◽  
Temperature And Humidity ◽  
The Difference ◽  
Cut Tobacco ◽  
Two Parameters

Nowadays most studies of drying processes dynamics are established on  empirical models without clear physical meanings, which could not predict the drying characteristic on different dryers. In order to describe the change of temperature and water content in the cut tobacco in different dryers, a mathematical model based on heat and mass transfer phenomena was developed, and the model employed the relationship of equilibrium moisture content and air humidity as basis, the difference of moisture between biomass and wet air as mass transfer driver, and the difference of temperature between biomass and wet air as heat transfer driver. The drying experiments under different air temperature and humidity are carried out on the batch rotary dryer, and the variance of temperature and moisture content in the biomass is obtained by using infrared thermometer and oven. The model is validated by two parameters with experiment data under each condition of air temperature and humidity. The results show that the drying dynamic model is well on accuracy and universality, and it could be applied on different drying device to predict the characteristic of kinds of drying processes.Keywords: cut tobacco; drying dynamics; equilibrium moisture content; heat transfer; mass transfer.   

scholarly journals Simulation analysis and optimization research on cooling and dehumidifying effects for evaporator

2020 ◽  
pp. 167-167
Author(s):  
Shuailing Liu ◽  
Guoyuan Ma ◽  
Shuxue Xu ◽  
Fuping Li ◽  
Chenzhe Hang
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Moisture Content ◽  
Linear Relationship ◽  
Air Temperature ◽  
Simulation Analysis ◽  
Evaporation Temperature ◽  
Temperature And Humidity ◽  
The Difference

The improvement performance of refrigerating dehumidification system was theoretically discusses based on a dehumidification model. The influence of evaporator inlet wind speed, dry bulb temperature and relative humidity on dehumidification were analysed by the model. The results show that, when inlet air temperature and humidity were kept constant, the dehumidification capacity increased first and then decreased with increase of the wind speed; When the moisture content and the wind speed of the inlet air were kept constant, the dehumidification capacity gradually decreased with increase of the inlet air dry bulb temperature; The inlet air dry bulb temperature was between 21-36 ?C and the relative humidity was between 40% and 85%, the difference between the inlet air wet bulb temperature and the evaporation temperature at the optimum COP was about 10 ?C; There was a nearly linear relationship between the corresponding evaporation temperature at the optimal COP and the evaporation temperature with the maximum dehumidification capacity, compared with the test value, the error was less than 10%.

scholarly journals Comparison of Building Simulation Methods for Modeling Apartment Balconies

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3955
Author(s):  
Yonghan Ahn ◽  
Hanbyeol Jang ◽  
Junghyon Mun
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Parameter Analysis ◽  
Interior Space ◽  
Heating And Cooling ◽  
Significant Difference ◽  
Calculation Results ◽  
Infiltration Parameter ◽  
The Difference ◽  
Heating And Cooling Load

The purpose of this study is to compare the load calculation results by a model using the air changes per hour (ACH) method and a model using an airflow network (AFN) and to ascertain what causes the difference between the two models. In the basic case study, the difference in the heat transfer distribution of the model in the interior space was investigated. The most significant difference between the two models is the heat transfer that results from infiltration. Parameter analysis was performed to investigate the relationship between the difference and the environmental variables. The result shows that the greater the difference is between the air temperature inside the balcony and the outdoor air temperature, and the greater the air flows from the balcony to the residential area, and the greater the heating and cooling load difference occurs. The analysis using the actual weather files of five domestic cities in South Korea rather than a virtual case shows that the differences are not so obvious when the wind blows at a constant speed throughout the year, but are dominant when the wind does not blow during the night and is stronger alongside the occurrence of sunlight during the day.

Heat and Mass Transfer Characteristics of a Finned-Tube Evaporator Under Frosting Conditions

2001 ◽  
Author(s):  
Y. H. Kim ◽  
Y. J. Park ◽  
Y. C. Kim ◽  
S. C. Shim ◽  
S. K. Oh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Air Temperature ◽  
Early Stage ◽  
Finned Tube ◽  
Airflow Rate ◽  
Air Velocity ◽  
Frost Formation ◽  
Transfer Characteristics

Abstract An experimental study was performed to investigate the heat and mass transfer characteristics of a finned-tube evaporator coil utilized in a domestic refrigerator under frosting conditions. Airside heat transfer coefficient was measured as a function of air temperature, humidity ratio, air velocity, and evaporating temperature. In addition, frost thickness was monitored and measured by visualization tests during frosting operation. Based on the experimental results, the degradation of heat transfer performance due to frost formation was explored as a function of operating parameters. The rate of frost formation on the evaporator increases at relatively high humidity, high airflow rate, low inlet air temperature and low refrigerant temperature. As the frost thickness increases, airflow rate gradually decreases, while the capacity increases at the early stage of frost formation and then significantly drops.

Experimental investigation for reverse heat transfer in structural fire-protective clothing

2016 ◽  
Vol 88 (5) ◽  
pp. 577-585
Author(s):  
Duck Weon Lee ◽  
Joon-Hyung Jin ◽  
Eunae Kim ◽  
Junghan Lee
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Thermal Effects ◽  
Protective Clothing ◽  
External Environment ◽  
Air Permeability ◽  
Outer Shell ◽  
Structural Fire ◽  
Multilayered Systems ◽  
The Difference

Structural fire-protective clothing must be effective at minimizing the thermal effects of fire. However, water remaining on the outer shell might play an important role in conducting heat transfer, which causes skin burns in a firefighter when he douses a fire with water through a hose. Therefore, this research demonstrated the difference in the heat transfer and humidity created by the remaining water or lack of water on the outer shell under a condition in which the temperature (45 ± 1℃) of the external environment was higher than that of the skin. Two types of multilayered systems, which simulated real fire-protective clothing (outer shell, moisture barrier, thermal liner) were tested by using a human–clothing–environment (HCE) simulator. The experimental results verified that water on the outer shell increased the microclimate temperature in the structural fire-protective clothing. In particular, we assume that air permeability in the outer shell can be an important factor to control heat and mass transfer within the microclimate.

A Heat-Mass Transfer Analogy Applied to Fully Developed Turbulent Flow in an Annulus

1971 ◽  
Vol 13 (4) ◽  
pp. 286-292 ◽  
Author(s):  
J. S. Lewis
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Friction Factor ◽  
Heat Mass Transfer ◽  
Eddy Diffusivity ◽  
Round Tube ◽  
Fully Developed Turbulent Flow ◽  
The Difference

A heat-mass transfer analogy based on the ‘universal’ velocity profile applied to an annulus is compared with analogy values based on similar but more sophisticated expressions for the eddy diffusivity and hence velocity profile. The difference between these analogy values and those of Chilton and Colburn (I)† are noted to be appreciable and to increase with increasing Reynolds number. Heat transfer predictions from mass transfer measurements using ‘universal’ velocity profile type analogies are compared with established results. Friction factor measurements were made and found to be up to 10 per cent higher than the values for flow in a round tube at the corresponding Reynolds number.

scholarly journals RANCANG BANGUN INSTRUMEN PENGUKUR SUHU DAN KELEMBAPAN UDARA MENGGUNAKAN DT-SENSE SHT11

2014 ◽  
Vol 14 (2) ◽  
pp. 113
Author(s):  
Imam Hidayat ◽  
Hesky Stevy Kolibu ◽  
Slamet Suyitno Raharjo
Keyword(s):  
Air Temperature ◽  
Low Cost ◽  
Measurement Instrument ◽  
Field Trials ◽  
Test Results ◽  
Standard Measurement ◽  
Humidity Measurement ◽  
Measurement Tools ◽  
Temperature And Humidity ◽  
The Difference

ABSTRAK Telah dilakukan pembuatan instumen pengukur suhu dan kelembapan udara menggunakan sensor DT-Sense SHT11 dan modul mikrokontroler DT-AVR Low Cost Micro System. Kemudian instrumen diuji dengan alat ukur standar. Pengujian dilakukan mulai bulan Juni 2013 dan berakhir bulan Oktober 2013di Laboratorium Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Sam Ratulangi Manado dan pengujian lapangan dilakukan di Stasiun Meteorologi Kelas II Maritim Bitung. Hasil pengujian dianalisis dengan metode grafik, analisis Korelasi dan Uji t sampel berpasangan. Hasilnya berhasil dibuat dengan ketelitian pengukuran hingga 0,01oC untuk pengukuran suhu udara dan 0,0001% untuk pengukuran kelembapan udara. Terdapat selisih antara instrumen yang dibuat dengan alat ukur standar. Rata-rata 1,4 oC untuk suhu udara dan 3% untuk kelembapan relatif. Kata kunci: sensor, mokrokontroler, SHT11   DESIGN AND BUILD OF AIR TEMPERATURE AND HUMIDITY MEASUREMENT INSTRUMENT USING DT-SENSE SHT11 ABSTRACT Have been made a temperature and humidity measurement instrument using DT-Sense sensor SHT11 and microcontroller modules DT-AVR Low Cost Micro System.‎ Then the instrument was tested with standard measurement tools. The tests were conducted starting in June 2013 and ended in October 2013 at the Laboratory of Physics, Faculty of Mathematics and Natural Sciences, Sam Ratulangi University and field trials conducted in Class II Meteorological Station Maritime Bitung. The test results were analyzed by graphical method, correlation analysis and paired sample t test.The result of measurement accuracy up to 0,01oC for measuring air temperature and up to 0,0001% for air humidity measuring. The difference between the instruments are made with standard measurement tools. An average of 1.4 ° C for temperature and 3% for relative humidity. Keywords: sensor, microcontroller, SHT11

scholarly journals Physicochemical Properties of Briquettes from Different Feed Stock

2015 ◽  
Vol 10 (1) ◽  
pp. 263-269 ◽  
Author(s):  
D Vyas ◽  
F Sayyad ◽  
M Khardiwar ◽  
Shailendra Kumar
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Chemical Properties ◽  
High Humidity ◽  
Feed Stock ◽  
Physico Chemical ◽  
Combustion Properties ◽  
Different Types ◽  
The Difference

This study was undertaken to evaluate the Physico-chemical properties of eight different types of biomass feed stock and their briquettes were studied among that some properties which are influence their storage and combustion properties like Equilibrium moisture content (EMC %) and Relative humidity (%). Equilibrium moisture content are found out by static equilibrium technique using aqueous glycerol solutions of different concentrations in the relative humidity (RH) range of 40 to 90 % and at ambient temperature between 25 to 37 ºC. The Equilibrium moisture content of briquettes was lower than their feedstock by about 1 – 2.5 % in all the cases ranges from 40 to 70 % RH. At higher RH above 70%, the difference was between 2 - 4%. There was no change in the shape of the briquettes at all levels of RH. This was due to higher density of briquettes. This study showed during period of high humidity, the storage of briquettes will not create any problem and will be safer as compared to their feedstock.

scholarly journals Processes of Heat and Mass Transfer During Grain Mass Storage in Metal Silos of Large Capacity

2021 ◽  
Author(s):  
Ivan Kechkin ◽  
Vladimir Ermolaev ◽  
Marina Belyaeva ◽  
Valentina Tarakanova ◽  
Elena Gurkovskaya ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Heat And Mass Transfer ◽  
Rate Of Change ◽  
Mass Storage ◽  
Large Capacity ◽  
Wheat Grains ◽  
Grain Moisture ◽  
Temperature And Humidity ◽  
Grain Temperature

This study showed that there were some changes in the temperature and humidity parameters of wheat grains during the storage year. The grain moisture content in both the near-wall and central parts of the metal silo largely did not change, remaining at a level of 10-11%. Moisture values were recorded monthly, and grain temperature was recorded in accordance with seasonal changes, thus, the range of temperature changes was from 20 to 32°С at a minimum outdoor temperature of 5°С. The moisture content of the grain in the surface layer increased by 0.4-1.2% and the final moisture content of the grain was 11.6%. Experiments on grain temperature and humidity changes with active ventilation in large-capacity metal silos have shown that the rate of change (decrease) in temperature depends on the specific air flow rate, and the difference in air and grain temperature. Experimental storage showed that a grain with the moisture content up to 13.6% can be stored for up to nine months without deterioration in quality. A longer shelf life is possible for wheat grains with a moisture content of up to 12%. This article pays special attention to the processes occurring in the under-roof space of large-capacity metal silos and suggests methods for solving this problem. Keywords: long-term storage, active ventilation, metal silos, heat and mass transfer processes

scholarly journals Heat of sorption and free energy change of freeze-dried pineapple pulp

1969 ◽  
Vol 77 (3-4) ◽  
pp. 101-111
Author(s):  
Humberto Vega-Mercado ◽  
Gustavo V. Barbosa-Cánovas
Keyword(s):  
Free Energy ◽  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Free Energy Change ◽  
Energy Change ◽  
Heat Of Sorption ◽  
Freeze Dried ◽  
Adsorption Data ◽  
Pineapple Pulp ◽  
Two Parameters

Two thermodynamic properties, the heat of sorption (Qs) and the Gibbs free energy change (∆G) were evaluated at several temperatures (5, 25, 30, 35 and 55°C) on freeze-dried pineapple pulp. It was found that 1) the heat of sorption follows the Clauslus-Clapeyron relationship; 2) the shape of the heat of sorption vs. the equilibrium moisture content curve was sigmoid; 3) the heat of sorption from adsorption data gave higher values than those from desorption data; and 4) the free energy change (∆G) is linearly related to the equilibrium moisture content. These two parameters are very important in dealing with food stability because it is possible to predict the water activity at any given temperature of either of these values is known.

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