The use of an absorption heat pump by a thermal bathing establishment

An energy saving plant was realized by a thermal bathing establishment. The plant is composed of a three fluid plate heat exchanger and an absorption heat pump between the source preheated water and the discharged one. During the cold winter the establishment is maintained at a temperature of 5°C. The absorption heat pump uses the thermal water as cold source.     

Thermodynamic modelling of absorption-resorption heating cycles with some new working pairs

This paper presents the results of a thermodynamic cycle analysis of single stage resorption heat pump (RHP) and resorption heat transformer (RHT) cycles with the new working pairs R22-NMP and R22-DMA. The coefficients of performance (COP) are correlated with the low grade source temperature, temperature at which useful heat is obtained and ambient temperature. The COPs are in the range 1.20–1.60 for the RHP mode and 0.25–0.45 for the RHT mode. Absorber temperatures (useful temperatures) as high as 50°C in the RHP mode and 87°C in the RHT mode have been obtained. It is observed that absorption-resorption systems are inflexible in their range of operating temperature and necessitate a higher pump work as compared with simple single-stage absorption heating systems. However, single stage RHTs show higher temperature boosts than simple absorption heat transformers.     

New compression heat pump media for medium and high temperature application

The economy and operability of compression heat pump systems is to a great extent influenced by the working fluid. However, the choice of the appropriate medium for a given heat pump application is not straight forward, since a great number of physical and non-physical properties of the presumptive working fluids have to be accounted for.A systematic method of looking for the best medium has been developed. With the help of a commercial flowsheet program a simulation routine of the heat pump cycle has been established. This routine was used to screen all substances in the attached data bank in respect to their applicability as working media. In all, 940 substances have been investigated. From these substances 42 show favourable properties as working fluids for the application in three cases, namely with a temperature of the heat source of 2°C and of the heat sink of 70°C respectively, 60°C source temperature and 120°C at the heat sink and of 90°C source temperature and 150°C at the heat sink.A further investigation of these 42 substances with respect to toxicity and stability left four of them as the ultimate proposal for operable compression heat pump fluids.Besides the actual proposal of new media, the investigation produces a much better understanding of the influence of physical properties on the heat pump performance. From the great number of data, a reliable prediction of the applicability of a given substance as a working fluid, based on the critical data, was deduced.     

Performance of a Single-Family Heat Pump at Different Working Conditions Using Small Quantity of Propane as Refrigerant

The performance of a domestic heat pump that uses a low quantity of propane as refrigerant has been experimentally investigated. The heat pump consists of two minichannel aluminium heat exchangers, a scroll compressor, and an electronic expansion valve. It was charged with the minimum amount of refrigerant propane required for the stable operation of the heat pump without permitting refrigerant vapor into the expansion valve at incoming heat source fluid temperature to the evaporator of +10°C. The inlet temperature of the heat source fluid passing through the evaporator was varied from +10°C to ?10°C while holding the condensing temperature constant at 35°C, 40°C, 50°C, and 60°C, respectively. The minimum refrigerant charges required at above-tested condensing temperatures were found to decrease when the condensing temperature increased and were recorded as 230 g, 224 g, 215 g, and 205 g, respectively. The results confirm that a heat pump with 5 kW capacity can be designed with less than 200 g charge of refrigerant propane in the system. Due to the high solubility of propane in compressor lubrication oil, the amount of refrigerant which may escape rapidly in case of accident or leakage is less than 150 g.     

Multi-stage structures for absorption heat pumps

Any absorption heat pump or heat transformer may be described as the association of two unit operations: the separation of a binary mixture in the desorber/condenser and the mixing of the separated components in the evaporator/absorber. Both the separator and the mixer can be constituted of a number of stages.In this paper a multi-stage absorption heat pump for air conditioning will be presented. The objective of this system is to exploit optimally the large temperature difference available for separation (240-35°C) and the rather small temperature lift for mixing (7°C–35°C) and at the same time to maximize the coefficient of performance. The system consists of a N-stage mixer functioning thermally in parallel and materially in series.Examples of multi-stage absorption heat pumps are given using the working fluids ammonia-sodium thiocyanate (NH₃NaSCN) and ammonia-lithium nitrate (NH₃LiNO₃). The advantages and disadvantages of these types of multi-stage systems are discussed.     

Study on the concentration difference heat pump using fusion and freezing processes of acetic acid-acetamide system

The concentration difference heat pump using fusion and freezing processes to generate a cold fluid has been investigated. This heat pump system utilizes the acetic acid-acetamide pair as working material, and consists of a cold fluid generating and a separation process. The operation at the cooling capacity of 3.52 kW (1 ton of refrigeration) has been investigated in this study. At the cold fluid generating process, solid acetic acid at 15°C is fused into an acetamide solution at 15°C, such that the temperature and the concentration of acetamide of the solution decreases. This dilute solution at lower temperature can be used to generate a cold fluid. The lowest attainable temperature of the solution has been investigated experimentally, and also calculated from the energy balance equation. The decreasing rates of the temperature have also been studied. At the separation process, continuous distillation is adopted to concentrate the dilute solution sent from the cold fluid generating process. The data which support the possibility of separation by continuous distillation are presented. The energy demand at the separation process is investigated theoretically.     

Experiments on an absorption refrigeration system powered by a solar pond

A heat source at temperatures not higher than 80°C was used to simulate the heat input to an absorption refrigerator from a solar pond. A laboratory model of an absorption refrigerator, using an ammonia-water solution at 52% concentration by weight, was operated intermittently using this heat source. Generation temperatures as high as 73°C and evaporation temperatures as low as −2°C were obtained. Tap water was used to remove the heat generated from the condensation of the ammonia vapour and the absorption of the refrigerant in the water. The temperature of the tap water was near the ambient laboratory temperature of 28°C. The COP for this unit working under such conditions was in the range 0.24–0.28.     

Gas turbine waste heat driven multiple effect absorption system

In this article, two arrangements of the multiple effect absorption (MEA) type are presented. They are using LiBr-H₂O and are powered by the exhaust of gas turbines. The first arrangement (MEA-I) is used as a cooling device and is coupled to an engine that drives a VC cooling unit. The other one (MEA-II) is used as a solution concentration machine and is coupled to an engine that drives a RO unit.Thermodynamic analysis for MEA-I showed a COP_t of 1.31 and 2.18 for evaporation temperatures of 5°C and 14°C respectively. Relative to the VC, the MEA-I increased the cooling capacity by 65% and 77% with payback periods of 35 months and 29 months for evaporation temperatures of 5°C and 14°C respectively.The MEA-II is analyzed using sea water as an example for a water based solution. Relative to a gas turbine driven RO desalination unit the MEA-II increased the fresh water produced by 13.5%. As a solution concentration machine the MEA-II requires 28% of the heat of evaporation with a solution top temperature of 36°C which makes it equivalent to a machine with five evaporators, where the solution top temperature reaches 66°C. Based on selling the released solvent byproduct water alone, the MEA-II would have a payback period of 77 months.     

Derived thermodynamic design data for heat pump systems operating on R152a

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R152a. These values are listed in tabular form for temperature lifts of 10–75°C and condensing temperatures of 20–85°C in 5°C increments. A composite plot has been drawn to illustrate the feasible operating range of R152a heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R170

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R170. These values are listed in tabular form for temperature lifts of 5–75°C and condensing temperatures of 6–31°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R170 heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R23

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R23. These values are listed in tabular form for temperature lifts of 5–75°C and condensing temperatures of 5–24°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R23 heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R1270

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R1270. These values are listed in tabular form for temperature lifts of 5–75°C and condensing temperatures of 12–90°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R1270 heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R744

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R503. These values are listed in tabular form for temperature lifts of 10–55°C and condensing temperatures of 7–30°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R744 heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R503

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R503. These values are listed in tabular form for temperature lifts of 5–75°C and condensing temperatures of 5–18°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R503 heat pump systems.     

Derived thermodynamic design data for heat pump systems operating on R13

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R13. These values are listed in tabular form for temperature lifts of 5–75°C and condensing temperatures of 6–26°C in one degree increments. A composite plot has been drawn to illustrate the feasible operating range of R13 heat pump systems.     

Mössbauer and magnetic studies on nanocrystalline NiFe2O4 particles prepared by ethylene glycol route

NiFe₂O₄ nanoparticles have been synthesized by co-precipitation method at 145°C in N₂ atmosphere using ethylene glycol as solvent and capping agent. This gives the promising synthesis route for nanoparticles at low temperature. The as-synthesized NiFe₂O₄ is subsequently heated at 400°C, 500°C, 700°C and 800°C. Crystallite size increases with the heat treatment temperature. The heat treatment temperature has direct effect on the electron paramagnetic resonance and intrinsic magnetic properties. The room temperature Mössbauer spectrum of the 800°C heated sample shows the two sextets pattern indicating that the sample is ferrimagnetic and Fe^3?+? ions occupy both tetrahedral and octahedral sites of spinel structure.     

Evaluation on the heat transfer performance of a vertical ground U-shaped tube heat exchanger buried in soil–polyacrylamide

Ground source heat pump (GSHP) systems have been applied widely because of their environmental-friendly, energy-saving, and sustainable nature. In this work, heat transfer performance of a single vertical small-scale U-shaped tube ground heat exchanger under hot climatic condition is addressed considering the influences of inlet water temperature, Reynolds number, and backfill materials (raw soil; soil–polyacrylamide (PAM) blend (0.27% blending ratio for PAM). The backfill materials had an important effect on the heat transfer of the ground heat exchanger. At an inlet water temperature of 45°C and Reynolds numbers of 3104 and 4656, the temperature drops of water in the tube in the soil–PAM blend increased by about 0.3 and 0.4°C compared to that in the raw soil. Within Reynolds number from 3104 to 6208, the average surface heat transfer coefficients of the water in the tube in the soil–PAM blend and raw soil at an inlet water temperature of 45°C were 411 and 231 W m^?2K^?1, respectively. The results suggest that adding the PAM into soil can be an effective manner for enhancing the heat transfer of the ground heat exchanger. The dimensionless surface heat transfer correlation of the water in the U-tube heat exchanger in the soil–PAM blend was obtained. The model could better fit the experimental data within ±10% deviation.     

High-stable,double-pass forward superfluorescent fiber source based on erbium-doped photonic crystal fiber

A double-pass forward configuration superfluorescent fiber source (SFS) based on erbium-doped photonic crystal fiber (EDPCF) with a high intrinsic mean wavelength stability is presented. The main factors of SFS instability with temperature variation are analyzed. Optimization of the high-stable SFS is achieved by combining high-performance EDPCF, optimal fiber length, and source structure with fine-tuning pump power. The temperature dependence of the SFS mean wavelength has been reduced to below 0.077 ppm/°C with temperature variation from 70 to ?40 °C. To the best of our knowledge, this value is the closest to 0 ppm/°C in the reported references, and these new developments probably constitute an important step for high-accuracy interferometric fiber-optic gyroscope sources.     

Thermo-frigopompe à absorption pour production simultanée de chaleur et de fraîcheur utiles

Absorption heat-cold-pump for simultaneous production of useful heat and coolness. A new absorption heat-cold-pump for the simultaneous production of useful cold (12 °C – 7 °C) and of useful heat (80 °C – 85 °C) is presented. The system operates with a couple of components with comparable volatilities, for example the following saturated hydrocarbons, butane + hexane, butane + octane, butane + decane, propane + octane. The working pair is separated in a rectification column. The components are remixed in a reverse-rectification column fitted with an incorporated heat exchanger. The COP and the exergy efficiency are presented for a number of modelized internal structures of the heat-cold-pump.     

Phase transition and copper ion conductor in PbBr2-CuBr

The solid solution of PbBr₂-CuBr has a high electric conductivity above 150 °C. The frequency and temperature dependences of complex dielectric constants have been investigated in the concentration of x=0.01-0.3. They exhibited a strong dieletric relaxation caused by the ionic conduction. Specific heat capacities have been measured in the temperature range from 100 to 200 °C. They showed no anomalous specific heat at the temperature 150 °C, but a distinct peak of heat was found at about 170 °C depending on the concentration. Using the simplified model of disorder of mobile ions, the excess specific heat was explained as the transition of copper ions between two sites. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997