The Experts below are selected from a list of 1488 Experts worldwide ranked by ideXlab platform

Jaeweon Jeong - One of the best experts on this subject based on the ideXlab platform.

  • Design and preliminary results of organic rankine cycle for Liquid Desiccant System
    Applied Thermal Engineering, 2020
    Co-Authors: Hye-won Dong, Jaeweon Jeong
    Abstract:

    Abstract In this study, the organic Rankine cycle (ORC)-based combined heat and power (CHP) System was developed and experimentally investigated to assess the feasibility of the application potential as an energy-efficient CHP System. This System harvests electrical energy from an unused district heat source and simultaneously provides heating for a Liquid Desiccant (LD)-assisted air-conditioning System. The working fluid selection is conducted considering its environmental impact under the operating conditions. When the maximum shaft power of ORC is 170.4 W under the tested condition, the thermal cycle efficiency is 4.5%. The ORC integrated with the LD (ORCLD) using Novec649 can provide a Desiccant solution over 50 °C without an auxiliary heater and achieve the maximum overall CHP efficiency of 79.1%. Consequently, it is found that Novec649 is a suitable working fluid for the ORC when simultaneously harvesting the energy from the unused district heat and providing the hot water to the LD, and the current design of the ORC CHP System is well adapted to the district heating System and LD unit.

  • energy saving potential of thermoelectric modules integrated into Liquid Desiccant System for solution heating and cooling
    Applied Thermal Engineering, 2018
    Co-Authors: Hansol Lim, Jaeweon Jeong
    Abstract:

    Abstract The main objective of this research was to investigate the impact thermoelectric modules (TEMs) integrated into a Liquid Desiccant (LD) System have on the heating and cooling of the Desiccant solution, and to evaluate the energy saving potential of the proposed System. Two TEM-integrated LD Systems were considered; in the first case (i.e., Case A), the TEMs accommodated the solution heating load at the regenerator and a portion of the solution cooling load at the absorber. The remaining solution cooling load was met by an auxiliary chiller. In the second case (i.e., Case B), the TEMs accommodated both the solution cooling and heating loads before the absorber and the regenerator, while extra heat released from the hot side of the TEMs was reclaimed and used to heat the scavenger air entering the regenerator. The conventional LD System, with a boiler and a chiller for heating and cooling the Desiccant solution, was also considered as a reference case, to evaluate the energy saving potential of both TEM-integrated LD Systems. Hourly energy consumption and temperature variation in the Desiccant solution in each System case were predicted via detailed energy simulation with existing mathematical and empirical models for each System component, such as the absorber, regenerator of LD, and TEMs. An approach for determining the required number of TEMs and the optimum temperature difference between the hot side and the cold side of the TEMs is also suggested, based on the coefficient of performance (COP) of the TEMs. It was found that a primary energy saving of about 2% could be expected in Case A compared with the reference case, whereas 55% more primary energy was consumed in Case B. Consequently, based on detailed energy simulations for the TEM-integrated LD System, it was found that the TEMs should be sized to accommodate the regeneration heating load of the Desiccant solution before the solution enters the regenerator. In this case, the cooling capacity of the TEMs would be insufficient for cooling the strong solution before the solution enters the absorber, and an auxiliary cooling device would be required.

  • Energy Saving Potential of a Thermoelectric Heat Pump-Assisted Liquid Desiccant System in a Dedicated Outdoor Air System
    Energies, 2017
    Co-Authors: Joonyoung Park, Jaeweon Jeong
    Abstract:

    The main objective of this study was to develop a thermoelectric heat pump and Liquid Desiccant System based on a dedicated outdoor air System (THPLD-DOAS). An internally-cooled and -heated Liquid Desiccant System was used and a thermoelectric heat pump (THP) served as the Desiccant cooling and heating energy source for dehumidification and regeneration of the Desiccant solution, respectively. In order to investigate the energy-saving potential of the proposed System, its thermal performance and operating energy consumption during the cooling season were compared to those of a conventional dedicated outdoor air System with a ceiling radiant cooling panel System (DOAS-CRCP). Detailed simulations for each System were conducted under hot and humid climatic conditions. Their thermal performance under various room sensible heat factor (RSHF) conditions was evaluated to observe the energy performance, depending on the dehumidification performance, of the Liquid Desiccant System integrated with the THP. The results showed that the coefficient of performance (COP) of the THP ranged from 0.8 to 1.2 to maintain a sufficient dehumidification rate. The operating energy of the THPLD of the proposed System was 6.6% to 16.0% less than that of the chiller operating energy of a conventional DOAS. Consequently, the proposed System consumed 0.6–23.5% less operating energy compared to the conventional DOAS.

  • Empirical model for predicting the dehumidification effectiveness of a Liquid Desiccant System
    Energy and Buildings, 2016
    Co-Authors: Joonyoung Park, Dong Seop Yoon, Sung-joon Lee, Jaeweon Jeong
    Abstract:

    Abstract The main purpose of this research was to propose a practical correlation for predicting the dehumidification effectiveness of a Liquid Desiccant (LD) System. The experimental data were collected during the operation of a typical Liquid Desiccant dehumidification unit. A lithium chloride (LiCl) solution was used as the Liquid Desiccant solution. The 2000 m3/h LD unit was installed in a real building, and the variation of the dehumidification effectiveness values was monitored under various operating conditions. The data were statistically analyzed by the response surface methodology (RSM), and the impact of each System operation parameter on the dehumidification effectiveness was estimated quantitatively. Six operating parameters – the mass flow rate of process air, the mass flow rate of the Desiccant solution, the dry-bulb temperature and the humidity ratio of the inlet air, and the inlet temperature and concentration of the Desiccant solution – significantly affected the dehumidification performance of the LD unit. Consequently, a simplified linear equation model was derived as a function of the operation parameters that significantly impacted the dehumidification effectiveness. The proposed model was verified by comparison with existing models.

  • simplified model for packed bed tower regenerator in a Liquid Desiccant System
    Applied Thermal Engineering, 2015
    Co-Authors: Joonyoung Park, Jaeweon Jeong
    Abstract:

    Abstract The regeneration rate prediction model representing the regenerator performance in a Liquid Desiccant System was derived by statistically analyzing the empirical data collected from the real Liquid Desiccant unit operated under various conditions. In order to propose a simple empirical regenerator model with wide valid range, additional experimental data found in open literature were also considered in the model derivation. The lithium chloride (LiCl) solution was used as a working Desiccant solution. Response surface methodology was used to identify operating parameters and their interactions affecting significantly on the regenerator performance in a Liquid Desiccant System. Consequently, a first-order linear regression equation was derived as a function of the major parameters and interactions, which returns the regeneration rate in various operating conditions. The reliability of the proposed model was confirmed via the analysis of variation (ANOVA). The proposed model agreed well with the experimental data and other existing models.

Alberto Coronas - One of the best experts on this subject based on the ideXlab platform.

  • Modeling and Dynamic Simulation of a Hybrid Liquid Desiccant System with Non-Adiabatic Falling-Film Air-Solution Contactors for Air Conditioning Applications in Buildings
    Energies, 2021
    Co-Authors: Juan Prieto, A Atienza-marquez, Alberto Coronas
    Abstract:

    This paper presents an experimentally validated, dynamic model of a hybrid Liquid Desiccant System. For this purpose, we developed new components for the air-solution contactors, which are of the non-adiabatic falling-film type with horizontal tubes (made of improved polypropylene) and the solution tanks. We also provide new experimental correlations for both the tube-solution heat transfer coefficient and the mass transfer coefficient on the airside as a function of the air velocity. To validate the model, the results obtained from the dynamic simulations were compared with those obtained by monitoring a demonstration unit installed in a sports center in Taipei (Taiwan). Once validated, the model was used to perform a sensitivity analysis at different operational conditions, such as the inlet water temperatures in the air-solution contactors and the LiCl mass fraction at which the System operates. The results of the sensitivity analysis were used to optimize the seasonal performance in terms of comfort and energy required by the System. Compared with a conventional air-handling unit that controls air temperature and humidity, the annual energy savings of the Liquid Desiccant Systems are 17%.

  • Modelling and dynamic simulation of a Liquid Desiccant System coupled to a heat pump for air conditioning.
    2019
    Co-Authors: J Prieto, A Atienza-marquez, Alberto Coronas
    Abstract:

    In applications where latent loads or ambient humidity are high, Liquid Desiccant Systems combined with vapor compression Systems are a suitable alternative to conventional HVAC Systems because they can efficiently control air temperature and humidity. In this sense, an optimal integration in terms of working conditions and energy management of both Systems is required in order to maximize the overall performance when they are coupled. This study analyses, by means of the modelling and dynamic simulation with TRNSYS, the seasonal performance of a Liquid Desiccant System coupled to a vapor compression heat pump for an HVAC application. The developed model is then used to optimize to overall performance in terms of energyconsumption and seasonal COP. Different operational conditions and control strategies are evaluated. Results show that evaporator/absorber and condenser/regenerator temperatures are the variables that mainly affect the seasonal COP of the System.

  • Experimental performance of polymeric air-solution contactors for Liquid Desiccant Systems
    Applied Thermal Engineering, 2017
    Co-Authors: Juan Prieto, Jordi Ortiga, Alberto Coronas
    Abstract:

    Abstract This paper evaluates the experimental performance of two falling-film absorbers with horizontal tubes of a Liquid Desiccant System. Both absorbers are made of polypropylene in order to avoid corrosion when the LiCl-H 2 O solution is in contact with them. To improve their wettability, and hence the heat and mass transfer, the tubes from one of the absorbers are subject to a plasma surface treatment. According to the experimental results, the inlet Liquid Desiccant temperature and air velocity are the variables that most affect the absorber performance. Therefore, these two variables can be used to control the supply humidity ratio and air cooling rate in a Liquid Desiccant System. Furthermore, in comparison with the absorber with untreated tubes, the absorber with treated tubes performed better in terms of the overall heat transfer coefficient (up to 54 %), the absorber heat duty (about 17%), the air cooling rate (up to 29%) and the dehumidification rate (20%).

  • Modelling and dynamic simulation of a hybrid Liquid Desiccant System regenerated with solar energy.
    Applied Thermal Engineering, 2016
    Co-Authors: Adriana Coca-ortegón, Juan Prieto, Alberto Coronas
    Abstract:

    The combination of Liquid Desiccant Systems with conventional vapour compression chillers, usually known as hybrid Liquid Desiccant Systems (HLDS), is a promising alternative when temperature and humidity need to be controlled in air conditioning applications. One of the advantages of this technology is that different kinds of energy can be integrated, particularly low temperature solar thermal energy, which can reduce the electrical consumption of the System. These kinds of Systems are typically analysed by discrete steady-state simulations, which show how the System behaves in design conditions. However, dynamic simulations can provide information about the seasonal performance and help to set an appropriate control strategy. This paper describes the modelling and dynamic simulation of an HLDS using Trnsys. Because there are non-standard components for the main elements of a Liquid Desiccant subSystem (LDS), an alternative modelling method based on performance tables has been developed. The simulation is carried out for Kuala Lumpur, a city with high humidity and ambient temperatures, where air conditioning is required throughout the year. The control strategy is also defined. Finally a sensitivity analysis is performed for the case analysed.

  • Experimental comparison between internally and externally cooled air-solution contactors
    Science and Technology for the Built Environment, 2015
    Co-Authors: Khaled Gommed, Jordi Ortiga, Gershon Grossman, Juan Prieto, Alberto Coronas
    Abstract:

    Air-conditioning demand, especially in hot and humid climates, causes most of the energy consumption in buildings. In these applications, the latent load often constitutes a significant part of the total load. Conventional air-conditioning Systems deal with the required dehumidification by cooling the moist air below its dew point and reheat it later to increase its temperature to comfortable supply conditions. By using solid/Liquid Desiccant Systems, which absorb humidity from the air, it becomes unnecessary to reach the dew point to dehumidify, thereby reducing energy consumption. In Liquid Desiccant Systems, dehumidification occurs in the absorber, where the humidity of the air is absorbed by direct contact with a Desiccant. Most of the previous Liquid Desiccant System studies have used adiabatic absorbers, where the solution must be cooled externally before being delivered into the air-solution contactor. However, based on experience with closed-cycle absorption Systems, internally cooled absorbers ar...

Khaled Gommed - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid Liquid Desiccant System design and operation under high latent load conditions in Taiwan
    International Journal of Refrigeration-revue Internationale Du Froid, 2019
    Co-Authors: Xabier Peña, Laura Alonso, Andoni Diaz De Mendibil, Juan Prieto, Khaled Gommed
    Abstract:

    Abstract Hybrid Liquid Desiccant Systems (HLDS) combine the Liquid Desiccant technology for dehumidification of air with conventional compression cycle technology for cooling. They are an alternative to conventional compression cooling Systems, being more efficient and offering the possibility of independently control temperature and humidity. In this paper the design and operation of a HLDS is presented, for the air conditioning of a high latent load application with high ambient humidity levels. An analysis of the daily evolution of the performance of the System under different environmental conditions has been included. The innovative demonstration unit placed in Taiwan, in continuous operation since November 2015, achieved Energy efficiency Ratios (EER) up to 4.6.

  • Efficient deep dehumidification hybrid air conditioning System
    International Journal of Refrigeration, 2019
    Co-Authors: Yigal Evron, Khaled Gommed, Gershon Grossman
    Abstract:

    Abstract Air conditioning (A/C) Systems serve two main functions: temperature and humidity control of the conditioned space. This work focuses on a hybrid A/C System consisting of a Liquid Desiccant System (LDS) and an absorption chiller. An efficient deep-dehumidification hybrid A/C System (EDHACS) configuration is proposed. It is designed to enhance both performance and control. A detailed simulation study of the EDHACS has been conducted, and selected results are described in this article. Liquid Desiccant Systems (LDS) are exceptionally good at air dehumidification, and hence capable of handling the latent heat load. In conventional air conditioning (A/C) Systems, this task is achieved by over-cooling the air below its dew point, which leads to both thermodynamic and practical inefficiencies. An optimal A/C System may be hybrid, consisting of a chiller to handle the sensible load and a low-grade heat driven Liquid-Desiccant-System (LDS), potentially with storage capability, to handle the latent load. The hybrid System has the added advantage of allowing independent control of temperature and humidity, thereby providing much-improved thermal comfort. Simulation results show that the EDHACS outperforms any other hybrid configuration that was tested. Its dehumidifier is split in two to take advantage of both the ambient and the chiller cooling capacity as heat sinks. By minimizing absorbent circulation between the two dehumidifiers, two distinct dehumidifier temperature levels are maintained, thereby further improving performance – resulting in increased COP and capacity values, and lower supply air temperatures.

  • Experimental comparison between internally and externally cooled air-solution contactors
    Science and Technology for the Built Environment, 2015
    Co-Authors: Khaled Gommed, Jordi Ortiga, Gershon Grossman, Juan Prieto, Alberto Coronas
    Abstract:

    Air-conditioning demand, especially in hot and humid climates, causes most of the energy consumption in buildings. In these applications, the latent load often constitutes a significant part of the total load. Conventional air-conditioning Systems deal with the required dehumidification by cooling the moist air below its dew point and reheat it later to increase its temperature to comfortable supply conditions. By using solid/Liquid Desiccant Systems, which absorb humidity from the air, it becomes unnecessary to reach the dew point to dehumidify, thereby reducing energy consumption. In Liquid Desiccant Systems, dehumidification occurs in the absorber, where the humidity of the air is absorbed by direct contact with a Desiccant. Most of the previous Liquid Desiccant System studies have used adiabatic absorbers, where the solution must be cooled externally before being delivered into the air-solution contactor. However, based on experience with closed-cycle absorption Systems, internally cooled absorbers ar...

  • Design, simulation and testing of a hybrid Liquid Desiccant for independent control of temperature and humidity
    2015
    Co-Authors: Laura Alonso, Jordi Ortiga, Xabier Peña, Juan Prieto, Carol Pascual, Khaled Gommed
    Abstract:

    In this paper the design, simulation and testing of a hybrid Liquid Desiccant System for a case study in Taiwan is presented, in the scope of the European project nanoCOOL. The designed System has been constructed and is being tested at laboratory scale. After the set-up of the System, it will be sent to Taipei for demonstration in real scale conditions, in the Taiwan Building Technology Center. The demonstration site comprises two locker rooms in a swimming pool of the university, with high internal humidity generation, low sensible heat ratio, and high external humidity levels due to sub-tropical humid climate present in Taiwan.

  • experimental investigation of a Liquid Desiccant System for solar cooling and dehumidification
    Solar Energy, 2007
    Co-Authors: Khaled Gommed, Gershon Grossman
    Abstract:

    Abstract Growing demand for air conditioning in recent years has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the environmentally-friendly techniques which may help alleviate the problem. A promising solar cooling method is through the use of a Liquid Desiccant System, where humidity is absorbed directly from the process air by direct contact with the Desiccant. The Desiccant is then regenerated, again in direct contact with an external air stream, by solar heat at relatively low temperatures. The Liquid Desiccant System has many potential advantages over other solar air conditioning Systems and can provide a promising alternative to absorption or to solid Desiccant Systems. Earlier work by the authors included theoretical simulations and preliminary experiments on the key components of the Liquid Desiccant System. The objective of the present study has been to construct a prototype System based on the knowledge gained, to monitor its performance, identify problems and carry out preliminary design optimization. A 16 kWt System was installed at the Energy Engineering Center at the Technion, in the Mediterranean city of Haifa. The System comprises a dehumidifier and a regenerator with their associated components operating together to dehumidify the fresh (ambient) air supply to a group of offices on the top floor of the building. LiCl-water is employed as the working fluid. The System is coupled to a solar collector field and employs two methods of storage – hot water and Desiccant solution in the regenerated state. The performance of the System was monitored for five summer months under varying operating conditions. The paper describes the operation of the experimental System and presents the measured data and the calculated performance parameters.

Gershon Grossman - One of the best experts on this subject based on the ideXlab platform.

  • Efficient deep dehumidification hybrid air conditioning System
    International Journal of Refrigeration, 2019
    Co-Authors: Yigal Evron, Khaled Gommed, Gershon Grossman
    Abstract:

    Abstract Air conditioning (A/C) Systems serve two main functions: temperature and humidity control of the conditioned space. This work focuses on a hybrid A/C System consisting of a Liquid Desiccant System (LDS) and an absorption chiller. An efficient deep-dehumidification hybrid A/C System (EDHACS) configuration is proposed. It is designed to enhance both performance and control. A detailed simulation study of the EDHACS has been conducted, and selected results are described in this article. Liquid Desiccant Systems (LDS) are exceptionally good at air dehumidification, and hence capable of handling the latent heat load. In conventional air conditioning (A/C) Systems, this task is achieved by over-cooling the air below its dew point, which leads to both thermodynamic and practical inefficiencies. An optimal A/C System may be hybrid, consisting of a chiller to handle the sensible load and a low-grade heat driven Liquid-Desiccant-System (LDS), potentially with storage capability, to handle the latent load. The hybrid System has the added advantage of allowing independent control of temperature and humidity, thereby providing much-improved thermal comfort. Simulation results show that the EDHACS outperforms any other hybrid configuration that was tested. Its dehumidifier is split in two to take advantage of both the ambient and the chiller cooling capacity as heat sinks. By minimizing absorbent circulation between the two dehumidifiers, two distinct dehumidifier temperature levels are maintained, thereby further improving performance – resulting in increased COP and capacity values, and lower supply air temperatures.

  • Experimental comparison between internally and externally cooled air-solution contactors
    Science and Technology for the Built Environment, 2015
    Co-Authors: Khaled Gommed, Jordi Ortiga, Gershon Grossman, Juan Prieto, Alberto Coronas
    Abstract:

    Air-conditioning demand, especially in hot and humid climates, causes most of the energy consumption in buildings. In these applications, the latent load often constitutes a significant part of the total load. Conventional air-conditioning Systems deal with the required dehumidification by cooling the moist air below its dew point and reheat it later to increase its temperature to comfortable supply conditions. By using solid/Liquid Desiccant Systems, which absorb humidity from the air, it becomes unnecessary to reach the dew point to dehumidify, thereby reducing energy consumption. In Liquid Desiccant Systems, dehumidification occurs in the absorber, where the humidity of the air is absorbed by direct contact with a Desiccant. Most of the previous Liquid Desiccant System studies have used adiabatic absorbers, where the solution must be cooled externally before being delivered into the air-solution contactor. However, based on experience with closed-cycle absorption Systems, internally cooled absorbers ar...

  • experimental investigation of a Liquid Desiccant System for solar cooling and dehumidification
    Solar Energy, 2007
    Co-Authors: Khaled Gommed, Gershon Grossman
    Abstract:

    Abstract Growing demand for air conditioning in recent years has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the environmentally-friendly techniques which may help alleviate the problem. A promising solar cooling method is through the use of a Liquid Desiccant System, where humidity is absorbed directly from the process air by direct contact with the Desiccant. The Desiccant is then regenerated, again in direct contact with an external air stream, by solar heat at relatively low temperatures. The Liquid Desiccant System has many potential advantages over other solar air conditioning Systems and can provide a promising alternative to absorption or to solid Desiccant Systems. Earlier work by the authors included theoretical simulations and preliminary experiments on the key components of the Liquid Desiccant System. The objective of the present study has been to construct a prototype System based on the knowledge gained, to monitor its performance, identify problems and carry out preliminary design optimization. A 16 kWt System was installed at the Energy Engineering Center at the Technion, in the Mediterranean city of Haifa. The System comprises a dehumidifier and a regenerator with their associated components operating together to dehumidify the fresh (ambient) air supply to a group of offices on the top floor of the building. LiCl-water is employed as the working fluid. The System is coupled to a solar collector field and employs two methods of storage – hot water and Desiccant solution in the regenerated state. The performance of the System was monitored for five summer months under varying operating conditions. The paper describes the operation of the experimental System and presents the measured data and the calculated performance parameters.

  • A Liquid Desiccant System for Solar Cooling and Dehumidification
    Journal of Solar Energy Engineering, 2004
    Co-Authors: Khaled Gommed, Gershon Grossman
    Abstract:

    The growing demand for air conditioning, particularly in hot and humid climates has caused a significant increase in demand for energy resources. A promising solar technology with potential to alleviate the problem is an open absorption System, where humidity is absorbed directly from the air to be treated by direct contact with the absorbent. The absorbent is then regenerated, again in direct contact with an external air stream, at relatively low temperatures of the heat source. The paper describes a study of a Liquid Desiccant cooling System designed to air-condition a group of offices on the top floor of a building in the Mediterranean city of Haifa, Israel. The System is capable of using as its source of power low-grade solar heat, of the type obtainable from low-cost flat plate collectors, and has a potential to provide both cooling and dehumidification in variable ratios, as required by the load. Several cycle variations have been considered, corresponding to different design options. A parametric study shows that entrance conditions of the ambient air significantly affect the heat and mass transfer occurring during the dehumidification process. The temperatures and flow rates of the heating and cooling water and the flow rates of solution through the dehumidifier and regenerator affect the humidity of the supply air delivered to the conditioned space, and show an optimum in certain cases.

Juan Prieto - One of the best experts on this subject based on the ideXlab platform.

  • Modeling and Dynamic Simulation of a Hybrid Liquid Desiccant System with Non-Adiabatic Falling-Film Air-Solution Contactors for Air Conditioning Applications in Buildings
    Energies, 2021
    Co-Authors: Juan Prieto, A Atienza-marquez, Alberto Coronas
    Abstract:

    This paper presents an experimentally validated, dynamic model of a hybrid Liquid Desiccant System. For this purpose, we developed new components for the air-solution contactors, which are of the non-adiabatic falling-film type with horizontal tubes (made of improved polypropylene) and the solution tanks. We also provide new experimental correlations for both the tube-solution heat transfer coefficient and the mass transfer coefficient on the airside as a function of the air velocity. To validate the model, the results obtained from the dynamic simulations were compared with those obtained by monitoring a demonstration unit installed in a sports center in Taipei (Taiwan). Once validated, the model was used to perform a sensitivity analysis at different operational conditions, such as the inlet water temperatures in the air-solution contactors and the LiCl mass fraction at which the System operates. The results of the sensitivity analysis were used to optimize the seasonal performance in terms of comfort and energy required by the System. Compared with a conventional air-handling unit that controls air temperature and humidity, the annual energy savings of the Liquid Desiccant Systems are 17%.

  • Hybrid Liquid Desiccant System design and operation under high latent load conditions in Taiwan
    International Journal of Refrigeration-revue Internationale Du Froid, 2019
    Co-Authors: Xabier Peña, Laura Alonso, Andoni Diaz De Mendibil, Juan Prieto, Khaled Gommed
    Abstract:

    Abstract Hybrid Liquid Desiccant Systems (HLDS) combine the Liquid Desiccant technology for dehumidification of air with conventional compression cycle technology for cooling. They are an alternative to conventional compression cooling Systems, being more efficient and offering the possibility of independently control temperature and humidity. In this paper the design and operation of a HLDS is presented, for the air conditioning of a high latent load application with high ambient humidity levels. An analysis of the daily evolution of the performance of the System under different environmental conditions has been included. The innovative demonstration unit placed in Taiwan, in continuous operation since November 2015, achieved Energy efficiency Ratios (EER) up to 4.6.

  • Experimental performance of polymeric air-solution contactors for Liquid Desiccant Systems
    Applied Thermal Engineering, 2017
    Co-Authors: Juan Prieto, Jordi Ortiga, Alberto Coronas
    Abstract:

    Abstract This paper evaluates the experimental performance of two falling-film absorbers with horizontal tubes of a Liquid Desiccant System. Both absorbers are made of polypropylene in order to avoid corrosion when the LiCl-H 2 O solution is in contact with them. To improve their wettability, and hence the heat and mass transfer, the tubes from one of the absorbers are subject to a plasma surface treatment. According to the experimental results, the inlet Liquid Desiccant temperature and air velocity are the variables that most affect the absorber performance. Therefore, these two variables can be used to control the supply humidity ratio and air cooling rate in a Liquid Desiccant System. Furthermore, in comparison with the absorber with untreated tubes, the absorber with treated tubes performed better in terms of the overall heat transfer coefficient (up to 54 %), the absorber heat duty (about 17%), the air cooling rate (up to 29%) and the dehumidification rate (20%).

  • Modelling and dynamic simulation of a hybrid Liquid Desiccant System regenerated with solar energy.
    Applied Thermal Engineering, 2016
    Co-Authors: Adriana Coca-ortegón, Juan Prieto, Alberto Coronas
    Abstract:

    The combination of Liquid Desiccant Systems with conventional vapour compression chillers, usually known as hybrid Liquid Desiccant Systems (HLDS), is a promising alternative when temperature and humidity need to be controlled in air conditioning applications. One of the advantages of this technology is that different kinds of energy can be integrated, particularly low temperature solar thermal energy, which can reduce the electrical consumption of the System. These kinds of Systems are typically analysed by discrete steady-state simulations, which show how the System behaves in design conditions. However, dynamic simulations can provide information about the seasonal performance and help to set an appropriate control strategy. This paper describes the modelling and dynamic simulation of an HLDS using Trnsys. Because there are non-standard components for the main elements of a Liquid Desiccant subSystem (LDS), an alternative modelling method based on performance tables has been developed. The simulation is carried out for Kuala Lumpur, a city with high humidity and ambient temperatures, where air conditioning is required throughout the year. The control strategy is also defined. Finally a sensitivity analysis is performed for the case analysed.

  • Experimental comparison between internally and externally cooled air-solution contactors
    Science and Technology for the Built Environment, 2015
    Co-Authors: Khaled Gommed, Jordi Ortiga, Gershon Grossman, Juan Prieto, Alberto Coronas
    Abstract:

    Air-conditioning demand, especially in hot and humid climates, causes most of the energy consumption in buildings. In these applications, the latent load often constitutes a significant part of the total load. Conventional air-conditioning Systems deal with the required dehumidification by cooling the moist air below its dew point and reheat it later to increase its temperature to comfortable supply conditions. By using solid/Liquid Desiccant Systems, which absorb humidity from the air, it becomes unnecessary to reach the dew point to dehumidify, thereby reducing energy consumption. In Liquid Desiccant Systems, dehumidification occurs in the absorber, where the humidity of the air is absorbed by direct contact with a Desiccant. Most of the previous Liquid Desiccant System studies have used adiabatic absorbers, where the solution must be cooled externally before being delivered into the air-solution contactor. However, based on experience with closed-cycle absorption Systems, internally cooled absorbers ar...