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Title: Separate sensible and latent cooling system: A preliminary analysis of a novel approach

Abstract

Separate sensible and latent cooling systems offer significant increases in the overall performance of cooling/dehumidification systems compared with conventional vapor-compression air-conditioning systems. Key to the energy efficiency of such systems is the performance of the heat and mass exchangers that provide sensible cooling and dehumidification. A novel design is proposed for dehumidification applications, deploying metal foam as a substrate coated with solid desiccants. The current report provides some preliminary information regarding the development of the technology and discusses factors such as manufacturing of desiccants, characterization of desiccants, and development of the metal foam heat exchanger. All three aspects provide the necessary infrastructure for further development and validation of the proposed concept.

Authors:
 [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1399928
Report Number(s):
ORNL/SPR-2017/479
102981
DOE Contract Number:
AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION

Citation Formats

Nawaz, Kashif. Separate sensible and latent cooling system: A preliminary analysis of a novel approach. United States: N. p., 2017. Web. doi:10.2172/1399928.
Nawaz, Kashif. Separate sensible and latent cooling system: A preliminary analysis of a novel approach. United States. doi:10.2172/1399928.
Nawaz, Kashif. 2017. "Separate sensible and latent cooling system: A preliminary analysis of a novel approach". United States. doi:10.2172/1399928. https://www.osti.gov/servlets/purl/1399928.
@article{osti_1399928,
title = {Separate sensible and latent cooling system: A preliminary analysis of a novel approach},
author = {Nawaz, Kashif},
abstractNote = {Separate sensible and latent cooling systems offer significant increases in the overall performance of cooling/dehumidification systems compared with conventional vapor-compression air-conditioning systems. Key to the energy efficiency of such systems is the performance of the heat and mass exchangers that provide sensible cooling and dehumidification. A novel design is proposed for dehumidification applications, deploying metal foam as a substrate coated with solid desiccants. The current report provides some preliminary information regarding the development of the technology and discusses factors such as manufacturing of desiccants, characterization of desiccants, and development of the metal foam heat exchanger. All three aspects provide the necessary infrastructure for further development and validation of the proposed concept.},
doi = {10.2172/1399928},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month =
}

Technical Report:

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  • A control strategy to reduce peak electric demand in small buildings was tested and evaluated. A test chamber designed to simulate the thermal response of a house was used in the experiments. The control strategy involved precooling the house before the onset of the peak and then controlling on humidity rather than temperature during the peak. A variant of the strategy substituted a low setpoint temperature and a limit on fractional on-time during the peak. Using this variant, the maximum on-peak demand was reduced by 35% while maintaining acceptable thermal comfort. Overall energy consumption was increased by 12%; means formore » eliminating this excess consumption are suggested for further evaluation.« less
  • Separate Sensible and Latent cooling (SSLC) has been discussed in open literature as means to improve air conditioning system efficiency. The main benefit of SSLC is that it enables heat source optimization for the different forms of loads, sensible vs. latent, and as such maximizes the cycle efficiency. In this paper I use a thermodynamic analysis tool in order to analyse the performance of various SSLC technologies including: multi-evaporators two stage compression system, vapour compression system with heat activated desiccant dehumidification, and integrated vapour compression with desiccant dehumidification. A primary coefficient of performance is defined and used to judge themore » performance of the different SSLC technologies at the design conditions. Results showed the trade-off in performance for different sensible heat factor and regeneration temperatures.« less
  • Separate sensible and latent cooling systems offer superior energy efficiency performance compared to conventional vapor compression air conditioning systems. In this paper we describe an innovative non-vapor compression system that uses electrochemical compressor (ECC) to pump hydrogen between 2-metal hydride reservoirs to provide the sensible cooling effect. The heat rejected during this process is used to regenerate the ionic liquid (IL) used for desiccant dehumidification. The overall system design is illustrated. The Xergy version 4C electrochemical compressor, while not designed as a high pressure system, develops in excess of 2 MPa (300 psia) and pressure ratios > 30. The projectedmore » base efficiency improvement of the electrochemical compressor is expected to be ~ 20% with higher efficiency when in low capacity mode due to being throttleable to lower capacity with improved efficiency. The IL was tailored to maximize the absorption/desorption rate of water vapor at moderate regeneration temperature. This IL, namely, [EMIm].OAc, is a hydrophilic IL with a working concentration range of 28.98% when operating between 25 75 C. The ECC metal hydride system is expected to show superior performance to typical vapor compression systems. As such, the combined efficiency gains from the use of ECC and separate and sensible cooling would offer significant potential savings to existing vapor compression cooling technology. A high efficiency Window Air Conditioner system is described based on this novel configuration. The system s schematic is provided. Models compared well with actual operating data obtained by running the prototype system. Finally, a model of an LiCl desiccant system in conjunction with the ECC-based metal hydride heat exchangers is provided.« less
  • A control strategy to reduce peak electric demand in small buildings was tested and evaluated. A test chamber designed to simulate the thermal response of a house was used in the experiments. The control strategy involved precooling the house before the onset of the peak and then controlling on humidity rather than temperature during the peak. A variant of the strategy substituted a low setpoint temperature and a limit on fractional on-time during the peak. Using this variant, the maximum on-peak demand was reduced by 35% while maintaining acceptable thermal comfort. Overall energy consumption was increased by 12%; means formore » eliminating this excess consumption are suggested for further evaluation.« less
  • This experimental study investigates the thermal hydraulic behavior and the heat removal performance for a scaled Reactor Cavity Cooling System (RCCS) with air. A quarter-scale RCCS facility was designed and built based on a full-scale General Atomics (GA) RCCS design concept for the Modular High Temperature Gas Reactor (MHTGR). The GA RCCS is a passive cooling system that draws in air to use as the cooling fluid to remove heat radiated from the reactor pressure vessel to the air-cooled riser tubes and discharged the heated air into the atmosphere. Scaling laws were used to preserve key aspects and to maintainmore » similarity. The scaled air RCCS facility at UW-Madison is a quarter-scale reduced length experiment housing six riser ducts that represent a 9.5┬░ sector slice of the full-scale GA air RCCS concept. Radiant heaters were used to simulate the heat radiation from the reactor pressure vessel. The maximum power that can be achieved with the radiant heaters is 40 kW with a peak heat flux of 25 kW per meter squared. The quarter-scale RCCS was run under different heat loading cases and operated successfully. Instabilities were observed in some experiments in which one of the two exhaust ducts experienced a flow reversal for a period of time. The data and analysis presented show that the RCCS has promising potential to be a decay heat removal system during an accident scenario.« less