Ammonia-Water Low-Temperature Thermal Storage System

1998 ◽  
Vol 120 (1) ◽  
pp. 25-31 ◽  
Author(s):  
J. J. Rizza
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Water Solution ◽  
Storage System ◽  
Water Concentration ◽  
Thermal Storage ◽  
Ammonia Vapor ◽  
Peak Period ◽  
Ammonia Water ◽  
Absorption Refrigeration System

An analysis of a low-temperature thermal storage system using an ammonia-water solution both as a refrigerant and as a low-temperature thermal storage material is considered. The thermal storage is useable at a temperature of −27°C and higher. The proposed system is designed to shift electric demand from high to low-demand periods. The system utilizes a heat-operated absorption refrigeration system; however, the generator heat is supplied by a self-contained vapor compression heat pump. The heat pump is operated during the off-peak period to recover the low-temperature thermal storage by reprocessing the stored ammonia-water solution to a lower ammonia-water concentration. The ammonia vapor liberated from solution in the dephlegmator is used in the compressor to produce the generator heat. Three different configurations are considered, including a solar-assisted system. The results are compared to an eutectic salt storage system.

Lithium Bromide and Water Thermal Storage System

1988 ◽  
Vol 110 (4) ◽  
pp. 327-334 ◽  
Author(s):  
J. J. Rizza
Keyword(s):  
Heat Pump ◽  
Liquid Water ◽  
Water Solution ◽  
Storage System ◽  
Lithium Bromide ◽  
Water System ◽  
Thermal Storage ◽  
Volumetric Efficiency ◽  
Peak Period ◽  
Water Ice

An analysis of a thermal storage system using a lithium bromide and water solution both as a refrigerant and as a storage material is considered. The proposed thermal storage system can be used to shift electric demand from periods of high demand to periods of low demand. The system is considered for both the summer cooling and winter heating season. The system’s evaporator and absorber are similar to that of a conventional heat-operated absorption refrigeration system; however, the generator heat is supplied by a self-contained electrically-driven vapor compression heat pump. The heat pump is operated during the off-peak period to recover the thermal storage by reprocessing the stored solution to a higher lithium bromide concentration. The water vapor liberated from solution in the generator is compressed and then condensed in the generator. The storage volumetric efficiency is determined and compared to storage systems based on water ice for the cooling season only and on a liquid water storage system for both cooling and heating. The storage volumetric efficiency of the proposed system is greater than or comparable to that of a thermal storage system based upon water ice and far exceeds the value for a thermal storage system based upon liquid water. The system can be constructed from standard HVAC components and appears to be a competitive alternative to a water ice storage system for summer cooling only, and it could be a competitive alternative to a liquid water system for combined summer and winter operations.

Experimental and Analytical Investigation of Ammonia Absorption into Ammonia-Water Solution: Estimated Interface Concentration

2010 ◽  
Vol 297-301 ◽  
pp. 785-789
Author(s):  
Hatem Mustafa
Keyword(s):  
Pressure Difference ◽  
Water Solution ◽  
Water System ◽  
Initial Pressure ◽  
Test Cell ◽  
Major Influence ◽  
Ammonia Vapor ◽  
Ammonia Water ◽  
Interface Concentration ◽  
Ammonia Absorption

Ammonia absorption process of ammonia vapor into ammonia water solution has been investigated experimentally, by inserting superheated ammonia vapor into a test cell containing a stagnant pool of ammonia water solution of several ammonia mass fractions, Ci. Before commencing the experiment, the pressure in the test cell corresponds to the equilibrium vapor of the ammonia-water system at room temperature. When the valve is opened, mechanical equilibrium is established quickly and the ammonia vapor diffuses into ammonia solution [1]. The difference between the initial pressure in the vapor cylinder and the initial pressure in the test cell ΔPi is found to have a major influence not only on the absorption rate but also on the estimated interface concentration. The interface concentration Cint of the cases ΔPi = 50 and 100 kPa exhibits a similar tendency, Cint decreases rapidly compared to other initial pressures ΔPi = 150 and 200 kPa. On the other hand, the interface concentration Cint of the cases ΔPi = 250 and 300 kPa are increasing within about 50 sec, then are hardly changing with time. They behave almost in a similar way as of Cint = 0.27 kg/kg. A correlation which gives the total absorbed mass of ammonia as a function of the initial concentration, the initial pressure difference and time is derived. In addition, the absorbed mass at no pressure difference could be estimated from the absorbed mass at initial pressure difference.

Aqueous Lithium Bromide TES and R-123 Chiller in Series

2003 ◽  
Vol 125 (1) ◽  
pp. 49-54 ◽  
Author(s):  
J. J. Rizza
Keyword(s):  
Heat Pump ◽  
Liquid Water ◽  
Lithium Bromide ◽  
Water System ◽  
Internal Heat ◽  
Thermal Storage ◽  
Volumetric Efficiency ◽  
Peak Period ◽  
Water Ice ◽  
In Series

This paper presents an analysis of a cold thermal energy storage (TES) system operating in series with an R-123 chiller. A lithium bromide/water LiBr/H2O solution is used both as a refrigerant and as a cold thermal storage material. The refrigerant, liquid water, is extracted from the LiBr/H2O strong solution during the off-peak period. The liquid water and LiBr/H2O weak solution, a byproduct of the refrigerant recovery process, are used during the on-peak period to cool the building. Building waste heat is pumped by the R-123 compressor to a higher temperature during the off-peak period and is used in the generator to recover the thermal storage by reprocessing the stored solution to a higher lithium bromide concentration. The storage volumetric efficiency and system COP are determined and compared to storage systems based on water/ice and liquid water. The storage volumetric efficiency is greater than a water/ice system and far exceeds the value for a liquid water system. The proposed system, which uses an external heat pump as a source of generator heat, is also compared to another LiBr/H2O system that uses a self-contained internal heat pump (the compressor operates independently from the chiller and uses the liberated water refrigerant as its working fluid). The system presented here outperforms both the water/ice system and the internal heat pump LiBr/H2O system but is unable to match the liquid water system COP. However, it has other well-defined advantages over the liquid water system and appears to be a competitive alternative to conventional TES systems.

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