Activated carbon (AC) has been widely utilized as adsorbent in adsorption refrigeration system for its high mass transfer performance, stable adsorption characteristics. However, its low thermal conductivity leads to long cycle time and small specific cooling power. In this paper, a new type of highly conductive composite activated carbon has been developed with the host matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA). Two adsorbers employing composite AC/ENG-TSA and composite AC/ expanded natural graphite (ENG) were produced by the cold-compression method and the adsorption performances were tested in an adsorption refrigeration system driven by low-pressure steam. To fit with the high thermal conductivity of the consolidated adsorbents, the shell-and-tube type adsorber was specially designed. In the adsorption system, the adsorber was heated by separate heat pipe and cooled by a closed cooling loop. The experimental results show that the adsorber employing composite AC/ENG-TSA has a better performance. The COP, SCP and volume refrigeration density of the refrigeration system are 0.103, 86.1 W/kg and 38.7 kW/m~3, respectively, under the following conditions: the temperature of heating source is 130 °C, the condensing temperature is 30 °C, the evaporation temperature is -5 °C, the cycle time 14 min. It was concluded that this kind of composite adsorbent was promising for adsorption refrigeration due to the great reduction of cycle time and significant improvement of specific cooling power.
展开▼
