ABSTRACT Composite adsorbents, comprising activated carbon and expanded natural graphite, have be... more ABSTRACT Composite adsorbents, comprising activated carbon and expanded natural graphite, have been developed, and their thermal conductivity, permeability and adsorption performance were tested. The thermal conductivity varied with the ratio of activated carbon to expanded natural graphite. Thermal conductivity increased as the ratio of expanded graphite increased. Considering that the density of activated carbon for the composite adsorbent should not be lower than 200 kg/m3, otherwise the volumetric cooling capacity would be unacceptably low, the highest thermal conductivity obtained from experiments was 2.47 W m−1 K−1. The permeability was also measured, and the best result obtained was 4.378 × 10−12 m2. In order to evaluate the influence of heat and mass transfer on adsorption performance, the adsorption rate was tested using a Rubotherm magnetic suspension balance, and results showed that for the freezing conditions lower than −10 °C the performance of granular activated carbon was better than that of solidified adsorbent because of the reduced mass transfer of ammonia at low saturated pressure. The adsorption performance of consolidated adsorbents increased rapidly when the evaporating temperature was higher than −10 °C. When the evaporating temperature was 8 °C, the adsorption rate of consolidated adsorbent was improved by 29% if compared with that of granular adsorbent.
... Available at: http://www.sorTech.de [accessed 20.11.09]. [6]; KK Khatri, D. Sharma, SL Soni, ... more ... Available at: http://www.sorTech.de [accessed 20.11.09]. [6]; KK Khatri, D. Sharma, SL Soni, D. Tanwar; Experimental investigation of CI engine operated micro-trigeneration system. Appl Therm Eng, 30 (2010), pp. 1505–1509. ...
Ammonia Activated carbon Modelling Performance COP Ice making Air conditioning Heat pump a b s t ... more Ammonia Activated carbon Modelling Performance COP Ice making Air conditioning Heat pump a b s t r a c t A thermodynamic cycle model is used to select an optimum adsorbent-refrigerant pair in respect of a chosen figure of merit that could be the cooling production (MJ m À3 ), the heating production (MJ m À3 ) or the coefficient of performance (COP). This model is based mainly on the adsorption equilibrium equations of the adsorbent-refrigerant pair and heat flows. The simulation results of 26 various activated carbon-ammonia pairs for three cycles (single bed, two-bed and infinite number of beds) are presented at typical conditions for ice making, air conditioning and heat pumping applications. The driving temperature varies from 80 C to 200 C. The carbon absorbents investigated are mainly coconut shell and coal based types in multiple forms: monolithic, granular, compacted granular, fibre, compacted fibre, cloth, compacted cloth and powder. Considering a two-bed cycle, the best thermal performances based on power density are obtained with the monolithic carbon KOH-AC, with a driving temperature of 100 C; the cooling production is about 66 MJ m À3 (COP ¼ 0.45) and 151 MJ m À3 (COP ¼ 0.61) for ice making and air conditioning respectively; the heating production is about 236 MJ m À3 (COP ¼ 1.50). ª 2009 Elsevier Ltd and IIR. All rights reserved. Les couples charbon actif-ammoniac pour les applications frigorifiques à adsorption: fabrication de glace, conditionnement d'air et pompes à chaleur Mots clés: Systè me à adsorption r e s u m e Un modè le du cycle thermodynamique est utilisé pour sé lectionner le meilleur couple adsorbant-ammoniac sur la base de la production frigorifique (MJ m À3 ), la production de (Z. Tamainot-Telto).
ABSTRACT A new type consolidated composite activated carbon (AC) was developed with a host matrix... more ABSTRACT A new type consolidated composite activated carbon (AC) was developed with a host matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA). Samples with different density, different grain size of AC, and different proportion of AC were produced and thermo-physical properties were evaluated. Results show that the highest effective thermal conductivity and thermal diffusivity of consolidated composite AC were 34.2Wm−1K−1 and 3.89×10−5m2s−1, which were 150 times and 72 times higher, respectively, than ordinary granular AC. The permeability of adsorbents ranged between 1.24×10−14 and 7.81×10−10m2 while the density ranged between 215 and 448kgm−3. The adsorption performance for composite AC and granular AC were evaluated by fitting experimental data with the equilibrium Dubinin–Astakhov (D–A) equations. Results show that the addition of ENG-TSA can improve the performance of adsorption refrigeration machines by increasing the concentration swing.
The thermal conductivity and permeability of consolidated expanded natural graphite treated with ... more The thermal conductivity and permeability of consolidated expanded natural graphite treated with sulphuric acid (ENG-TSA) were measured both parallel and perpendicular to the direction of compression used to produce the samples. Results showed that the thermal conductivity and permeability were highly anisotropic. The thermal conductivity perpendicular to the direction of compression was 50 times higher than that parallel to the
ABSTRACT Two types of host for activated carbon (AC) adsorbents intended for use in compressed sy... more ABSTRACT Two types of host for activated carbon (AC) adsorbents intended for use in compressed systems are studied: expanded natural graphite (ENG) and expanded natural graphite treated with acid (ENG-TA). Results show that compressed ENG-TA has much higher thermal conductivity than the compressed ENG. For a density of 830 kg/m3 the thermal conductivity of compressed ENG-TA is 336 W/(mK), and it is of the order of one hundred times higher compared with compressed ENG having similar density. The permeability of compressed ENG-TA is much more critical than the compressed ENG. For example for similar density of 300 kg/m3, the permeability of compressed ENG-TA is 2.01 × 10−15 m2 while the permeability of compressed ENG is 1.07 × 10−13 m2. Compressed composite adsorbents of AC with ENG as host were produced with a high density in the range 700–720 kg/m3. Considering that the permeability will be too low using composite AC with ENG-TA as host in high density, the density range was restricted to less than 500 kg/m3. The thermal conductivity of AC/ENG-TA composite is much higher than the thermal conductivity of AC/ENG composite, and it is about 7 times higher than the optimal value of AC/ENG composite.
Chemisorption could be useful in adsorption systems due to the large concentration change compare... more Chemisorption could be useful in adsorption systems due to the large concentration change compared with physisorption. Equilibrium concentration characteristics of ammonia with a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) are investigated: the maximum concentration is about 0.4 kg ammonia/kg adsorbent. Hysteresis was observed between the synthesis and the decomposition reactions. The analysis of the data suggests that the hysteresis could be due to the dimensional changes of the solid during the reactions. The bi-variant behaviour observed was contrary to the mono-variant behaviour anticipated and the reasons are discussed. The COP of a basic adsorption cycle for typical ice-making and air-conditioning applications utilizing ammonia and the composite material were calculated. The results show that the material could be used for air-conditioning or other refrigeration applications. The COP could reach up to 0.6 at typical conditions (T ev = 15°C, T con = 35°C).
To obtain accurate kinetics of adsorption pairs, dynamic tests of a composite adsorbent material ... more To obtain accurate kinetics of adsorption pairs, dynamic tests of a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) and ammonia were performed on small samples under isothermal conditions and on a larger quantity in a laboratory scale adsorption system. The experimental results show that the size of the pressure swing plays an important role in the dynamics of adsorption pairs. This driving pressure difference affects the mass transfer of NH 3 through the pores of adsorbent and therefore the performance of the complete adsorption system. A modified Linear Driving Force (LDF) model was used to fit the experimental results. It was shown that the model can predict the dynamics of both adsorption and desorption fairly well and can be used for the modelling of the adsorption system and adsorption cycles.
Novel composite sorbent ''31 wt.% CaCl 2 /ACF" was synthesised by dry impregnation of an ACF felt... more Novel composite sorbent ''31 wt.% CaCl 2 /ACF" was synthesised by dry impregnation of an ACF felt with a CaCl 2 aqueous solution. Apparent isosters of ammonia sorption were measured at T = 20-90°C and P = 0.1-9.0 bar by an isosteric adsorption method. The method is based on the sorbent heating in a closed volume of an adsorber with registration of the ammonia equilibrium pressure P as a function of temperature T. The uptake covered the range of 5.7-36.9 wt.%. The apparent enthalpy and entropy of the ammonia sorption as a function of ammonia uptake were obtained directly from the slop of isosteric lines lnP(1/T). Appropriate correction to obtain the true sorption enthalpy was done by taking into account the ''dead" volume of the adsorber. The new adsorbent was found to be an advanced material for adsorptive chilling. (M.M. Tokarev).
ABSTRACT Composite adsorbents, comprising activated carbon and expanded natural graphite, have be... more ABSTRACT Composite adsorbents, comprising activated carbon and expanded natural graphite, have been developed, and their thermal conductivity, permeability and adsorption performance were tested. The thermal conductivity varied with the ratio of activated carbon to expanded natural graphite. Thermal conductivity increased as the ratio of expanded graphite increased. Considering that the density of activated carbon for the composite adsorbent should not be lower than 200 kg/m3, otherwise the volumetric cooling capacity would be unacceptably low, the highest thermal conductivity obtained from experiments was 2.47 W m−1 K−1. The permeability was also measured, and the best result obtained was 4.378 × 10−12 m2. In order to evaluate the influence of heat and mass transfer on adsorption performance, the adsorption rate was tested using a Rubotherm magnetic suspension balance, and results showed that for the freezing conditions lower than −10 °C the performance of granular activated carbon was better than that of solidified adsorbent because of the reduced mass transfer of ammonia at low saturated pressure. The adsorption performance of consolidated adsorbents increased rapidly when the evaporating temperature was higher than −10 °C. When the evaporating temperature was 8 °C, the adsorption rate of consolidated adsorbent was improved by 29% if compared with that of granular adsorbent.
... Available at: http://www.sorTech.de [accessed 20.11.09]. [6]; KK Khatri, D. Sharma, SL Soni, ... more ... Available at: http://www.sorTech.de [accessed 20.11.09]. [6]; KK Khatri, D. Sharma, SL Soni, D. Tanwar; Experimental investigation of CI engine operated micro-trigeneration system. Appl Therm Eng, 30 (2010), pp. 1505–1509. ...
Ammonia Activated carbon Modelling Performance COP Ice making Air conditioning Heat pump a b s t ... more Ammonia Activated carbon Modelling Performance COP Ice making Air conditioning Heat pump a b s t r a c t A thermodynamic cycle model is used to select an optimum adsorbent-refrigerant pair in respect of a chosen figure of merit that could be the cooling production (MJ m À3 ), the heating production (MJ m À3 ) or the coefficient of performance (COP). This model is based mainly on the adsorption equilibrium equations of the adsorbent-refrigerant pair and heat flows. The simulation results of 26 various activated carbon-ammonia pairs for three cycles (single bed, two-bed and infinite number of beds) are presented at typical conditions for ice making, air conditioning and heat pumping applications. The driving temperature varies from 80 C to 200 C. The carbon absorbents investigated are mainly coconut shell and coal based types in multiple forms: monolithic, granular, compacted granular, fibre, compacted fibre, cloth, compacted cloth and powder. Considering a two-bed cycle, the best thermal performances based on power density are obtained with the monolithic carbon KOH-AC, with a driving temperature of 100 C; the cooling production is about 66 MJ m À3 (COP ¼ 0.45) and 151 MJ m À3 (COP ¼ 0.61) for ice making and air conditioning respectively; the heating production is about 236 MJ m À3 (COP ¼ 1.50). ª 2009 Elsevier Ltd and IIR. All rights reserved. Les couples charbon actif-ammoniac pour les applications frigorifiques à adsorption: fabrication de glace, conditionnement d'air et pompes à chaleur Mots clés: Systè me à adsorption r e s u m e Un modè le du cycle thermodynamique est utilisé pour sé lectionner le meilleur couple adsorbant-ammoniac sur la base de la production frigorifique (MJ m À3 ), la production de (Z. Tamainot-Telto).
ABSTRACT A new type consolidated composite activated carbon (AC) was developed with a host matrix... more ABSTRACT A new type consolidated composite activated carbon (AC) was developed with a host matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA). Samples with different density, different grain size of AC, and different proportion of AC were produced and thermo-physical properties were evaluated. Results show that the highest effective thermal conductivity and thermal diffusivity of consolidated composite AC were 34.2Wm−1K−1 and 3.89×10−5m2s−1, which were 150 times and 72 times higher, respectively, than ordinary granular AC. The permeability of adsorbents ranged between 1.24×10−14 and 7.81×10−10m2 while the density ranged between 215 and 448kgm−3. The adsorption performance for composite AC and granular AC were evaluated by fitting experimental data with the equilibrium Dubinin–Astakhov (D–A) equations. Results show that the addition of ENG-TSA can improve the performance of adsorption refrigeration machines by increasing the concentration swing.
The thermal conductivity and permeability of consolidated expanded natural graphite treated with ... more The thermal conductivity and permeability of consolidated expanded natural graphite treated with sulphuric acid (ENG-TSA) were measured both parallel and perpendicular to the direction of compression used to produce the samples. Results showed that the thermal conductivity and permeability were highly anisotropic. The thermal conductivity perpendicular to the direction of compression was 50 times higher than that parallel to the
ABSTRACT Two types of host for activated carbon (AC) adsorbents intended for use in compressed sy... more ABSTRACT Two types of host for activated carbon (AC) adsorbents intended for use in compressed systems are studied: expanded natural graphite (ENG) and expanded natural graphite treated with acid (ENG-TA). Results show that compressed ENG-TA has much higher thermal conductivity than the compressed ENG. For a density of 830 kg/m3 the thermal conductivity of compressed ENG-TA is 336 W/(mK), and it is of the order of one hundred times higher compared with compressed ENG having similar density. The permeability of compressed ENG-TA is much more critical than the compressed ENG. For example for similar density of 300 kg/m3, the permeability of compressed ENG-TA is 2.01 × 10−15 m2 while the permeability of compressed ENG is 1.07 × 10−13 m2. Compressed composite adsorbents of AC with ENG as host were produced with a high density in the range 700–720 kg/m3. Considering that the permeability will be too low using composite AC with ENG-TA as host in high density, the density range was restricted to less than 500 kg/m3. The thermal conductivity of AC/ENG-TA composite is much higher than the thermal conductivity of AC/ENG composite, and it is about 7 times higher than the optimal value of AC/ENG composite.
Chemisorption could be useful in adsorption systems due to the large concentration change compare... more Chemisorption could be useful in adsorption systems due to the large concentration change compared with physisorption. Equilibrium concentration characteristics of ammonia with a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) are investigated: the maximum concentration is about 0.4 kg ammonia/kg adsorbent. Hysteresis was observed between the synthesis and the decomposition reactions. The analysis of the data suggests that the hysteresis could be due to the dimensional changes of the solid during the reactions. The bi-variant behaviour observed was contrary to the mono-variant behaviour anticipated and the reasons are discussed. The COP of a basic adsorption cycle for typical ice-making and air-conditioning applications utilizing ammonia and the composite material were calculated. The results show that the material could be used for air-conditioning or other refrigeration applications. The COP could reach up to 0.6 at typical conditions (T ev = 15°C, T con = 35°C).
To obtain accurate kinetics of adsorption pairs, dynamic tests of a composite adsorbent material ... more To obtain accurate kinetics of adsorption pairs, dynamic tests of a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) and ammonia were performed on small samples under isothermal conditions and on a larger quantity in a laboratory scale adsorption system. The experimental results show that the size of the pressure swing plays an important role in the dynamics of adsorption pairs. This driving pressure difference affects the mass transfer of NH 3 through the pores of adsorbent and therefore the performance of the complete adsorption system. A modified Linear Driving Force (LDF) model was used to fit the experimental results. It was shown that the model can predict the dynamics of both adsorption and desorption fairly well and can be used for the modelling of the adsorption system and adsorption cycles.
Novel composite sorbent ''31 wt.% CaCl 2 /ACF" was synthesised by dry impregnation of an ACF felt... more Novel composite sorbent ''31 wt.% CaCl 2 /ACF" was synthesised by dry impregnation of an ACF felt with a CaCl 2 aqueous solution. Apparent isosters of ammonia sorption were measured at T = 20-90°C and P = 0.1-9.0 bar by an isosteric adsorption method. The method is based on the sorbent heating in a closed volume of an adsorber with registration of the ammonia equilibrium pressure P as a function of temperature T. The uptake covered the range of 5.7-36.9 wt.%. The apparent enthalpy and entropy of the ammonia sorption as a function of ammonia uptake were obtained directly from the slop of isosteric lines lnP(1/T). Appropriate correction to obtain the true sorption enthalpy was done by taking into account the ''dead" volume of the adsorber. The new adsorbent was found to be an advanced material for adsorptive chilling. (M.M. Tokarev).
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