https://orcid.org/0000-0002-7396-9782
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ABSTRACT
Adsorption heat pump (AdHP) is a potential technology to recover and storage low-temperature waste heat. This paper presents an experimental research on direct low-pressure process steam generation from hot water based on superhydrophobic surface-modified zeolite 13X. The measured water contact angle of the modified zeolite is larger than 150°, which restricts free water entering the pores inside the zeolite particles. Cyclic experiments are conducted for performance evaluation. High-temperature steam (205–229°C, 0.1–0.3 MPa) is generated from hot water (72°C) in the AdHP driven by dry air (130°C). The temperature of generated steam is promoted with increasing preset steam pressure, among which the temperature is raised by about 23°C at 0.3 MPa. As the boiling point of water rises simultaneously, the sensible heat demand is increased. Thus, the mass of the steam is accordingly decreased. GTL (gross temperature lift) reaches 130°C. When the preset pressure is increased, COPh (coefficient of performance for heating) and SHP (specific heat power) for direct steam generation are decreased by 36% and 39%, respectively. One feasible option to elevate these two indicators is to increase the inlet water to near boiling water to match the change in the preset pressure. However, the GTL will be decreased based on the option. Balance should be made based on the choice of design for practical application.
Nomenclature
| Symbols used | = | |
| m | = | mass [kg] |
| Q | = | heat quantity [kJ] |
| T | = | temperature [°C] |
| t | = | time [s] |
| x | = | water content [g/g] |
| cp | = | specific heat capacity [kJ/(kg·K)] |
| ∆H | = | adsorption heat [kJ/kg] |
| Greek letters | = | |
| γ | = | latent heat of water [kJ/kg] |
| Sub- and superscripts | = | |
| w,in | = | inlet water |
| s,out | = | generated steam |
| drain | = | water discharged from reactor |
| acc | = | accumulated free water |
| r | = | reactor |
| z | = | zeolite |
| z,dry | = | dry zeolite |
| ads | = | adsorption |
| reg | = | regeneration |
| z+r | = | zeolite and reactor |
| ref | = | reference |
| bp | = | boiling point |
| s | = | steam |
| fin | = | final stage |
| ini | = | initial stage |
| w | = | water |
| g | = | inlet gas during regeneration |
| max | = | maximum |
| eq | = | equilibrium |
| eq’ | = | equilibrium in high preset pressure phase |
| sat | = | saturated |
| zs | = | zeolite and steam |
| zw | = | zeolite and water |
| Abbreviations | = | |
| AdHPs | = | adsorption heat pumps |
| COP | = | coefficient of performance |
| SHP | = | specific heating power [kW/kg] |
| GTL | = | gross temperature lift [℃] |
Disclosure statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
CRediT authorship contribution statement
Xiaoran He: Conceptualization, Methodology, Writing-Review. & Editing.
Ruixun Wei: Investigation, Validation, Visualization.
Ali Jan: Supervision.
Guangyao Li : Methodology, Visualization.
Tingting Chen: Data curation, Formal analysis.
Bing Xue: Funding acquisition, Investigation, Writing-Review & Editing.
Additional information
Funding
Notes on contributors
Xiaoran He
Xiaoran He is currently pursuing her PhD at Kyushu University, Japan. She graduated in July 2023 with a Master's degree in Chemical Engineering from Zhengzhou University. Her research interests are enhancement of adsorption heat pumps and preparation of adsorbent materials.
Ruixun Wei
RuiXun Wei is currently pursuing a master's degree in Materials and Chemical Engineering at Zhengzhou University. He received his bachelor's degree from Huaqiao University. His research interest is mainly in the development and application of binder-free zeolite materials.
Ali Jan
Ali Jan is an international student from Pakistan. He is currently pursuing a Master's degree in Materials and Chemical Engineering at Zhengzhou University. His research interest is in the simulation of adsorption refrigeration.
Guangyao Li
Guangyao Li is currently pursuing his PhD at Kyushu University, Japan. He graduated in July 2022 with a Master's degree in Power Engineering from Zhengzhou University. His research interests are preparation of superhydrophobic zeolite and enhancement of adsorption heat pump.
Tingting Chen
Tingting Chen graduated in July 2022 with a Master's degree in Chemical Engineering from Zhengzhou University. She earned her bachelor's degree from Zhengzhou University of Light Industry. Her research interests are manily in preparation and modification of composite adsorbent materials.
Bing Xue
Bing Xue is currently an associate professor at the College of Chemical Engineering, Zhengzhou University. He has obtained his Ph.D. from Kyushu University, Japan. He has teaching and research experience of more than ten years. His main research interests include low-grade heat utilization, adsorption heat pump, and preparation of binder-free zeolite-based composite adsorbents.