Limits of mass transfer enhancement in lithium bromide-water absorbers by active techniques

Bor Bin Tsai, Horacio Perez-Blanco

    Research output: Contribution to journalArticle

    21 Citations (Scopus)

    Abstract

    A model to predict the theoretical limits of mass transfer enhancement in a falling film absorber using LiBr aqueous solution has been developed and it provides a means of comparative absorber performance evaluation. During vapor absorption, the vapor-liquid interface becomes saturated immediately after it is exposed to vapor. Further absorption can only be sustained by mass diffusion and heat conduction into the fluid bulk, assuming a stationary interface. Due to the relatively small heat and mass diffusivities of LiBr aqueous solution, the mass absorption rates, mixing of the solution is favored. Therefore, every mass transfer enhancement technique, passive or active, consists of basically disturbing the film and cuasing mixing of the solution near the interface. The higher the mixing rate, the higher the mass absorption rate. To assess the effect of a mixed interface, a mathematical model is formulated. This model solves one-dimensional heat and mass differential equations coupled at the interface. As asymptote of the mass transfer rate as the mixing rate increases is derived. The model, which takes into account all relevant parameters such as temperatures, pressure, concentrations, mass flow rates, and geometry, is an ideal tool for rating absorber performance. Results show that, under typical operating conditions found in commercial chillers, the theoretically possible maximum mass absorption rate is 0.049 kg m2.s-1, and that, at a mechanically feasible mixing frequency of 1000 Hz, a mass absorption rate of 0.0256 kg m2.s-1 is possible. The latter rate is about an order of magnitude larger than that found in commercial chillers.

    Original languageEnglish (US)
    Pages (from-to)2409-2416
    Number of pages8
    JournalInternational Journal of Heat and Mass Transfer
    Volume41
    Issue number15
    DOIs
    StatePublished - Aug 1 1998

    Fingerprint

    mass transfer
    bromides
    absorbers
    Lithium
    Mass transfer
    lithium
    Water
    augmentation
    water
    Vapors
    Heat conduction
    vapors
    aqueous solutions
    flow geometry
    Differential equations
    heat
    liquid-vapor interfaces
    asymptotes
    Flow rate
    lithium bromide

    All Science Journal Classification (ASJC) codes

    • Condensed Matter Physics
    • Mechanical Engineering
    • Fluid Flow and Transfer Processes

    Cite this

    @article{7bddb810e7f04588b057f76cf8b09cef,
    title = "Limits of mass transfer enhancement in lithium bromide-water absorbers by active techniques",
    abstract = "A model to predict the theoretical limits of mass transfer enhancement in a falling film absorber using LiBr aqueous solution has been developed and it provides a means of comparative absorber performance evaluation. During vapor absorption, the vapor-liquid interface becomes saturated immediately after it is exposed to vapor. Further absorption can only be sustained by mass diffusion and heat conduction into the fluid bulk, assuming a stationary interface. Due to the relatively small heat and mass diffusivities of LiBr aqueous solution, the mass absorption rates, mixing of the solution is favored. Therefore, every mass transfer enhancement technique, passive or active, consists of basically disturbing the film and cuasing mixing of the solution near the interface. The higher the mixing rate, the higher the mass absorption rate. To assess the effect of a mixed interface, a mathematical model is formulated. This model solves one-dimensional heat and mass differential equations coupled at the interface. As asymptote of the mass transfer rate as the mixing rate increases is derived. The model, which takes into account all relevant parameters such as temperatures, pressure, concentrations, mass flow rates, and geometry, is an ideal tool for rating absorber performance. Results show that, under typical operating conditions found in commercial chillers, the theoretically possible maximum mass absorption rate is 0.049 kg m2.s-1, and that, at a mechanically feasible mixing frequency of 1000 Hz, a mass absorption rate of 0.0256 kg m2.s-1 is possible. The latter rate is about an order of magnitude larger than that found in commercial chillers.",
    author = "Tsai, {Bor Bin} and Horacio Perez-Blanco",
    year = "1998",
    month = "8",
    day = "1",
    doi = "10.1016/S0017-9310(97)00287-1",
    language = "English (US)",
    volume = "41",
    pages = "2409--2416",
    journal = "International Journal of Heat and Mass Transfer",
    issn = "0017-9310",
    publisher = "Elsevier Limited",
    number = "15",

    }

    Limits of mass transfer enhancement in lithium bromide-water absorbers by active techniques. / Tsai, Bor Bin; Perez-Blanco, Horacio.

    In: International Journal of Heat and Mass Transfer, Vol. 41, No. 15, 01.08.1998, p. 2409-2416.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Limits of mass transfer enhancement in lithium bromide-water absorbers by active techniques

    AU - Tsai, Bor Bin

    AU - Perez-Blanco, Horacio

    PY - 1998/8/1

    Y1 - 1998/8/1

    N2 - A model to predict the theoretical limits of mass transfer enhancement in a falling film absorber using LiBr aqueous solution has been developed and it provides a means of comparative absorber performance evaluation. During vapor absorption, the vapor-liquid interface becomes saturated immediately after it is exposed to vapor. Further absorption can only be sustained by mass diffusion and heat conduction into the fluid bulk, assuming a stationary interface. Due to the relatively small heat and mass diffusivities of LiBr aqueous solution, the mass absorption rates, mixing of the solution is favored. Therefore, every mass transfer enhancement technique, passive or active, consists of basically disturbing the film and cuasing mixing of the solution near the interface. The higher the mixing rate, the higher the mass absorption rate. To assess the effect of a mixed interface, a mathematical model is formulated. This model solves one-dimensional heat and mass differential equations coupled at the interface. As asymptote of the mass transfer rate as the mixing rate increases is derived. The model, which takes into account all relevant parameters such as temperatures, pressure, concentrations, mass flow rates, and geometry, is an ideal tool for rating absorber performance. Results show that, under typical operating conditions found in commercial chillers, the theoretically possible maximum mass absorption rate is 0.049 kg m2.s-1, and that, at a mechanically feasible mixing frequency of 1000 Hz, a mass absorption rate of 0.0256 kg m2.s-1 is possible. The latter rate is about an order of magnitude larger than that found in commercial chillers.

    AB - A model to predict the theoretical limits of mass transfer enhancement in a falling film absorber using LiBr aqueous solution has been developed and it provides a means of comparative absorber performance evaluation. During vapor absorption, the vapor-liquid interface becomes saturated immediately after it is exposed to vapor. Further absorption can only be sustained by mass diffusion and heat conduction into the fluid bulk, assuming a stationary interface. Due to the relatively small heat and mass diffusivities of LiBr aqueous solution, the mass absorption rates, mixing of the solution is favored. Therefore, every mass transfer enhancement technique, passive or active, consists of basically disturbing the film and cuasing mixing of the solution near the interface. The higher the mixing rate, the higher the mass absorption rate. To assess the effect of a mixed interface, a mathematical model is formulated. This model solves one-dimensional heat and mass differential equations coupled at the interface. As asymptote of the mass transfer rate as the mixing rate increases is derived. The model, which takes into account all relevant parameters such as temperatures, pressure, concentrations, mass flow rates, and geometry, is an ideal tool for rating absorber performance. Results show that, under typical operating conditions found in commercial chillers, the theoretically possible maximum mass absorption rate is 0.049 kg m2.s-1, and that, at a mechanically feasible mixing frequency of 1000 Hz, a mass absorption rate of 0.0256 kg m2.s-1 is possible. The latter rate is about an order of magnitude larger than that found in commercial chillers.

    UR - http://www.scopus.com/inward/record.url?scp=0032146706&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=0032146706&partnerID=8YFLogxK

    U2 - 10.1016/S0017-9310(97)00287-1

    DO - 10.1016/S0017-9310(97)00287-1

    M3 - Article

    AN - SCOPUS:0032146706

    VL - 41

    SP - 2409

    EP - 2416

    JO - International Journal of Heat and Mass Transfer

    JF - International Journal of Heat and Mass Transfer

    SN - 0017-9310

    IS - 15

    ER -