Abstract
A full scale lab prototype of an adsorptive heat transformer (AHT), consisting of two adsorbers, an evaporator, and a condenser, was designed and tested in subsequent cycles of heat upgrading. The composite LiCl/SiO2 was used as an adsorbent with methanol as an adsorbtive substance under boundary temperatures of TL/TM/TH = −30/20/30 °C. Preliminary experiments demonstrated the feasibility of the tested AHT in continuous heat generation, with specific power output of 520 W/kg over 1–1.5 h steady-state cycling. The formal and experimental thermal efficiency of the tested rig were found to be 0.5 and 0.44, respectively. Although the low potential heat to be upgraded was available for free from a natural source, the electric efficiency of the prototype was found to be as high as 4.4, which demonstrates the promising potential of the “heat from cold” concept. Recommendations for further improvements are also outlined and discussed in this paper.
Highlights
Adsorptive heat transformation (AHT) is an energy-saving and environmentally friendly technology that is attracting increasing attention due to its ability to effectively convert and store waste or renewable heat [1,2,3]
The heat from cold” (HeCol) cycle consists of two isosteres (1-2, 3-4) and two isotherms (2-3, 4-1), and operates between three thermostats at low (TL ), middle (TM ), and high (TH ) temperatures (Figure 1)
The novelty of the HeCol cycle is that the adsorbent regeneration is initiated by the drop in vapor pressure over the adsorbent down to PL (4 → 1), whereas in the common adsorptive heat transformer (AHT) desorption is driven by the adsorbent heating
Summary
Adsorptive heat transformation (AHT) is an energy-saving and environmentally friendly technology that is attracting increasing attention due to its ability to effectively convert and store waste or renewable heat [1,2,3]. The novelty of the HeCol cycle is that the adsorbent regeneration is initiated by the drop in vapor pressure over the adsorbent down to PL (4 → 1), whereas in the common AHT desorption is driven by the adsorbent heating For this purpose, the condenser is maintained at low temperature (TL ), while the adsorbent is maintained at middle temperature TM and the heat for desorption is used for free from the natural heat source. The useful heat generation proceeds isothermally at high cycle temperature TH (2 → 3) and is initiated by vapor pressure increase to PM At this stage, the evaporator is kept at middle temperature; heat for evaporation comes from the natural heat source.
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