Performance of adsorbent-embedded heat exchangers using binder-coating method. (January 2016)

• Record Type: Journal Article
• Authors: Li, Ang; Thu, Kyaw; Ismail, Azhar Bin; Shahzad, Muhammad Wakil; Ng, Kim Choon
• Is Part Of: International journal of heat and mass transfer. Volume 92(2016:Jan.)
• Page Start: 149
• Page End: 157
• Publication Date: 2016-01
• Subjects: Silica gel–water -- Adsorption heat transfer -- Adsorption isotherms -- Binder -- Hydroxyethyl cellulose; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2015.08.097
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: A binder-blended coating method to embed silica gel onto heat exchanger fins is presented. HEC is most suitable for silica gel–water pairs among several tested binders. Heat transfer rates are 3.4–4.6 folds higher over the conventional granular-packing method. Water transport rate is 1.5–2 times faster. Significant improvement of the COP, reduction on plant size and cost of conventional adsorption chillers can be realized. Abstract: The performance of adsorption (AD) chillers or desalination cycles is dictated by the rates of heat and mass transfer of adsorbate in adsorbent-packed beds. Conventional granular-adsorbent, packed in fin-tube heat exchangers, suffered from poor heat transfer in heating (desorption) or cooling (adsorption) processes of the batch-operated cycles, with undesirable performance parameters such as higher footprint of plants, low coefficient of performance (COP) of AD cycles and higher capital cost of the machines. The motivation of present work is to mitigate the heat and mass "bottlenecks" of fin-tube heat exchangers by using a powdered-adsorbent cum binder coated onto the fin surfaces of exchangers. Suitable adsorbent–binder pairs have been identified for the silica gel adsorbent with pore surface areas up to 680 m 2 /g and pore diameters less than 6 nm. The parent silica gel remains largely unaffected despite being pulverized into fine particles of 100 μm, and yet maintaining its water uptake characteristics. The paper presents an experimental study on the selection and testing processes to achieve high efficacy of adsorbent–binder coated exchangers. The test results indicate 3.4–4.6 folds improvement in heat transfer rates over the conventional granular-packed method, resulting a faster rate of water uptake by 1.5–2 times on the suitable silica gel type.