Effects Of Generation Temperature Research Articles

Effect of generator temperature on steam ejector performance in renewable refrigeration cycle considering wet steam model and dry steam model

The rise in global warming has led to an increased utilization of cooling systems. High energy consumption associated with common refrigeration cycles not only contributes to air pollution but also intensifies the consumption of fossil fuels. Consequently, the imperative to conserve energy has become paramount in today's world. One of the methods to decrease energy consumption involves employing systems capable of harnessing waste heat from industries, solar energy, and other sources. The ejector refrigeration cycle (ERC) stands as an example of such systems. In present study, the impact of elevating the generator temperature on various aspects such as flow behavior in the ejector, aerodynamic shocks, entrainment ratio (ER), and entropy production was examined. The investigation encompassed both wet steam model (WSM) and dry steam model (DSM). Based on the findings, it was observed that with an increase in generator temperature, the ER decreases while the production entropy increases. In the WSM, the liquid mass fraction (LMF) also experiences an increase. Additionally, the Mach number distribution in the DSM surpasses that of the WSM and the temperature drop in the DSM is greater compared to the WSM. With the rise in generator temperature from 388 K to 418 K, both the DSM and WSM exhibit a decrease in ER by 52.9% and 58.7%, respectively. Furthermore, the production entropy experiences a substantial increase of 180% and 206% for the DSM and WSM, respectively.

The performance of [Emim]Br/H2O as a working pair in the absorption refrigeration system

The energy efficiency of the single-effect absorption refrigeration systems (ARS) using ionic liquid (IL) [Emim]Br as an absorbent and water as a refrigerant is evaluated in this study. The thermodynamic properties of the mixture, such as vapor pressures and excess enthalpies, are calculated using the non-random two-liquid (NRTL) activity coefficient model. The coefficient of performance (COP) is estimated with fixed temperatures for the evaporator, absorber, condenser, and generator, set at 10, 30, 40, and 100 °C, respectively. It is found that the COP of the single-effect ARS using [Emim]Br-H2O as the working pair is about 0.8, which is slightly lower than that obtained with LiBr-H2O (0.83), but much higher than that of H2O-NH3 (0.65) systems. The effect of generator temperature on COP has the same trend as that of other IL working pairs. The influence of each component temperature on the system’s performance is investigated, and it is found that the single-effect ARS performs very well under different conditions with [Emim]Br - H2O as the working pair.

Thermodynamic analysis of H2O − 3-aminopropyl tributyl phosphonium glycinate as a working pair for absorption refrigeration system

In this paper, A hydrophilic dual amino-functionalized ionic liquid 3-aminopropyl tributyl phosphonium glycinate ([aP4443][Gly]) with high thermal stability was used as absorbent and the refrigerant was water for the absorption refrigeration system (ARS). The heat capacities of the system were estimated by the differential scanning calorimetry (DSC) with various water mass fractions (w1) (0.004 to 0.6993) and temperatures (285 K to 365 K), and a polynomial equation on temperature and mass fraction of ionic liquid (w2) was associated. Between the experimental and estimated values, the average relative deviation (ARD) was 0.66%. The vapor–liquid equilibrium (VLE) data of the H2O–[aP4443][Gly] binary mixture was correlated using the electrolyte nonrandom two-liquid (eNRTL) model, and the binary mixture's excess thermodynamic properties were simulated. The first and second laws of thermodynamics were used to simulate the performance of a single-effect ARS with a solution heat exchanger (SHE). The ARS simulation results show that the coefficient of performance (COP) of the system with H2O–[aP4443][Gly] as the working pair is higher than that of the conventional working pair NH3-H2O but slightly lower than that of H2O-LiBr. Furthermore, the effect of generator temperature (Tg) on ARS is investigated; simulation results show that the ARS of the novel working pair has a higher COP value at higher generator temperature, indicating that H2O–[aP4443][Gly] has the potential to be a new type of absorption refrigeration working pair.

Energy and exergy analysis of proposed compression-absorption refrigeration assisted by a heat-driven turbine at low evaporating temperature

Abstract The thermal performances of proposed compression-absorption refrigeration assisted by a heat-driven turbine (CRHT) at low evaporating temperature were numerically investigated. According to the ideal isentropic process and the isentropic efficiency, the mathematical models of the micro tube and the compressors are built up. The CRHT system was modeled and simulated by considering the mass conservation, energy conservation, mechanical power conservation, and exergy generation equation of each component. For the case of basic design, the operating parameters, energy balance and the total thermal conductance of each component are calculated and analyzed. The effects of generation temperature, evaporating temperature of R134a, ammonia mass fraction of NH3/H2O, and compression ratios on thirteen key operating parameters were simulated and discussed. The COP of the CRHT system is compared with those of the two-stage absorption refrigeration system and the heat-driven compression-absorption refrigeration system in literatures, which proves that the proposed CRHT system possesses the best thermal performance. The exergy losses of each component were calculated and compared. It is indicated that the heat transfer areas of components should be optimized appropriately.

Experimental Investigation of the Effect of Generator Temperature on the Performance of Solution Transportation Absorption Chiller

It is effective to recover waste heat to reduce primary energy consumption. From this point of view, we proposed and examined a new idea of heat transportation using ammonia–water as the working fluid in the system named the Solution Transportation Absorption chiller (STA). As waste heat sources are not necessarily located close to areas of heat demand, conventionally, absorption chillers are located on heat source side and produce chilled water that is transported to heat demand side through pipelines with an insulation. In contrast, the proposed system STA divides an absorption chiller into two parts. The generator and the condenser are located on heat source side while the evaporator and the absorber are on heat demand side. Both the conventional system and STA system satisfy the same boundary condition of heat recovery and heat supply to the demand side, STA can work for transferring thermal energy as the conventional system does even though the temperature of the media is ambient without an insulation. Our previous studies of the STA were based on the experimental investigation with the STA facility where the cooling power was 90[Formula: see text]kW (25.6 refrigeration ton) at the generator temperature 120[Formula: see text]C from 0[Formula: see text]m (normal absorption chiller) to 1000[Formula: see text]m. Thus, the Coefficient of Performance (COP) of STA was found to have almost the same value of 0.65 with conventional absorption chillers without depending on the transportation distances. The objective of this study is to examine the effect of generator temperature from 100[Formula: see text]C to 120[Formula: see text]C on the performance of solution transportation of ammonia–water solution, because the generator temperature is directly linked to the waste heat temperature, so its effect needs to be investigated. The experimental facility tested the performance with 0[Formula: see text]m (normal absorption chiller), 200[Formula: see text]m and 500[Formula: see text]m distance. The results indicate that the effect of the generator temperature and solution transportation distances showed no significant on the COP.

Exergo-economic analysis of a solar driven hybrid storage absorption refrigeration cycle

This paper presents the exergo-economic analysis of a 5kW refrigeration cycle with hybrid storage system. The novel hybrid storage comprises a cold (ice) storage tank, an ammonia storage tank, a weak solution tank and a strong solution tank to suffice the nighttime cooling load. The exergo-economic analysis is performed to compare the components of the refrigeration cycle based on the costs of initial capital investment and the costs of irreversibilities. The components of the refrigeration cycle are evaluated and compared using exergo-economic variables such as the relative cost difference, exergy destruction cost rate and exergo-economic factor. The effect of generator temperature, condenser temperature and evaporator temperature on the exergetic efficiency of the system is also studied. The paper also presents a quasi-steady exergy and exergo-economic analysis for a representative summer day of Dhahran region. This study can be further used in the optimization of design variables of the studied refrigeration cycle.

Thermodynamic analysis of a Rankine cycle powered vapor compression ice maker using solar energy.

To develop the organic Rankine-vapor compression ice maker driven by solar energy, a thermodynamic model was developed and the effects of generation temperature, condensation temperature, and working fluid types on the system performance were analyzed. The results show that the cooling power per square meter collector and ice production per square meter collector per day depend largely on generation temperature and condensation temperature and they increase firstly and then decrease with increasing generation temperature. For every working fluid there is an optimal generation temperature at which organic Rankine efficiency achieves the maximum value. The cooling power per square meter collector and ice production per square meter collector per day are, respectively, 126.44 W m−2 and 7.61 kg m−2 day−1 at the generation temperature of 140°C for working fluid of R245fa, which demonstrates the feasibility of organic Rankine cycle powered vapor compression ice maker.

Performance analysis and working fluids selection of solar powered organic Rankine-vapor compression ice maker

To develop the organic Rankine cycle/vapor compression cycle (ORC/VCC) ice maker driven by solar energy, a thermodynamic model was developed, and four working fluids of R123, R245fa, R600a and R600 were selected and evaluated to identify suitable working fluids which may yield high system efficiencies. Besides, the effects of generation temperature and condensation temperature on the system performance were also analyzed. In terms of power efficiency and expander size, R600 and R600a are more suitable working fluids for ORC. Also, R600a and R600 are more appropriate working fluids for VCC in terms of pressure ratio and coefficient of performance. In terms of overall efficiency and ice production per square meter collector per day, R123 is most suitable working fluid for ORC/VCC. The generation temperature and condensation temperature have important effects on overall efficiency and ice production. There is always an optimal generation temperature at which overall efficiency and ice production can achieve the maximum values, while the generation temperature can be controlled by changing the mass flow rate of working fluid for ORC. In addition, the system performance and payback period should be comprehensively considered so as to decide to adopt air cooled or water cooled condenser due to having different condensation temperature.