Part Load Conditions Research Articles

Experimental comparison and seasonal performance evaluation of different scroll compressor capacity modulation methods in an R410A water to water system

Rising cooling needs for the residential and commercial air conditioning sectors and the demand for higher SEER require HVAC&R to handle cooling loads below the design condition. Although several studies exist focusing on a particular capacity modulation strategy, there is no extensive study that explores all these available modulation strategies in the same experimental facility. This study experimentally compared a single speed, a two-stage compressor, tandem combinations of two single speed compressors, a single speed and two-stage compressor, and a variable speed compressor using the same R410A water ethylene glycol (WEG) system for cooling application. These modulation strategies were tested according to AHRI Standard 551/591 (2020), and their seasonal performance is given by Integrated Part Load Value (IPLV.SI). A two-stage compressor with lower LMTD at the heat exchangers and a single speed compressor with higher isentropic efficiency have the same performance at one of the part load conditions. Additionally, a single speed compressor with an improved compressor motor has a 3% higher IPLV.SI than a two-stage compressor with the baseline motor. Different methods of interpolation that are available when the capacity is in between two compressor stages of operation were discussed. The tandem combinations with different number of stages have the same seasonal performance, showing that not all the stages available might be useful. The variable speed compressor with the best IPLV.SI was selected to further study the performance under heating application using EU 14825 (2013) standard with constant and variable condenser outlet conditions. For heating application, variable speed compressor with a wider range of modulation is recommended when selecting the compressor for variable condenser outlet temperature conditions while it might not be the best option due to compressor operating envelope limitation when operating with constant condenser temperature outlet.

Simulation of the Performance of an Electrically Turbocharged Engine Over an Urban Driving Cycle

The study aimed to estimate the energy recovery potential of a decoupled electric turbocharger and its boosting ability in a spark-ignition engine using simulation-based work. Passenger vehicle engines operate at low loads and speeds, requiring characterization and estimation of energy available for recovery under normal driving conditions. A 1-D numerical model of the engine and boosting system was developed to predict energy recovery over steady-state full-load operating conditions, part-load conditions, and actual, transient Klang Valley and Kuala Lumpur drive cycle conditions. The electric turbocharged engine consists of two motors and a battery pack, which were modeled and utilized using GT-Power engine simulation software. The study found that the electrical turbocharger system could recover 0.57 kW and 0.50 kW at 2500 rpm and 3000 rpm, respectively. Part-load studies showed that the maximum amount of electrical energy recovered at 6500 rpm was 5.25 kW. Drive cycle analysis revealed that fuel consumption was the same for both engine models due to the similar turbocharger output performance and lower back pressure caused by the recalibrated wastegate controller. This was partially mitigated by the inclusion of two electric motors. Drive cycle analysis revealed that the electric turbocharger can perform better than a conventional turbocharger when optimized.

Seasonal performance assessment and experimental investigation of R32 drop-in and BPHX size in an R410A chiller when using two compressor modulation strategies

The decrease in fossil fuel reserves and high energy consumption by HVAC&R equipment require the use of compressors with better efficiencies and capacity modulation strategies. Usually, seasonal performance studies focus on compressor capacity modulation methods, however the current study explores the idea of improving the seasonal performance of two compressor modulation techniques: a two-stage and a variable speed compressor with different capacity modulation ranges by using larger condensers in an R410A water ethylene glycol chiller system. The analysis shows that oversizing the heat exchangers has larger benefits with the compressor modulation strategy with lower range. Additionally, the seasonal performance estimated according to AHRI 551/591 (2020) of a two-stage compressor with oversized condenser is higher than a basic single speed compressor with a better motor indicating that oversizing brazed plate heat exchanger (BPHX) might yield higher performance than improving the compressor motor efficiency. Due to the high global warming potential (GWP) of R410A, there is a focus on replacing it with low GWP refrigerants such as R32 to reduce CO2 emissions. This study would also compare the performance when using R32 as a drop-in refrigerant in the two different R410A compressor capacity modulation strategies with comparable cooling capacity. When the refrigerant was changed from R410A to R32, the integrated part load value (IPLV.SI), an efficiency metric for variable speed compressor remains relatively constant at 5.5 while it increases from 3.9 to 4.4 for the two-stage compressor. It is hypothesized that low refrigerant mass flow rate (m˙ref) provided by the variable speed compressor when matching the load at the lower part load conditions leads to refrigerant maldistribution in BPHX and reduced IPLV.SI.

Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation

The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load operation is particularly detrimental since the development of a rotating vortical structure termed rotating vortex rope (RVR) in the draft tube leads to periodic pressure pulsations that jeopardize turbine performance. This paper experimentally explores a novel solution involving the protrusion of flat plates into the turbine draft tube. Three flat plates equally separated by 120° were vertically installed on the draft tube wall. The plates were protruded up to 83% of the draft tube local radius under four different part-load conditions. Their impact was observed through time-resolved pressure measurements in the draft tube and vaneless space, as well as efficiency measurements. The results demonstrated successful RVR mitigation, achieving a maximum 85% reduction in pressure oscillation amplitudes. Protruding flat plates disrupted RVR periodicity and coherence, confining its orbit to the draft tube center. This approach proved particularly effective at lower part-load conditions, enhancing turbine hydraulic efficiency by increasing torque extraction. Reducing the adverse effects under part load, the proposed method appears promising in extending the operational range of hydraulic turbines.

Two-phase flow investigation of sewage pumps with different tip clearance via computational fluid dynamics and multi-factor ANOVA

Sewage pumps are widely utilized in various applications, including municipal wastewater treatment plants, industrial processes, and residential sewage systems. These pumps are specifically designed to handle the transportation of mixtures consisting of solid and liquid components, commonly observed as two-phase flow. In this study, semi-open sewage pumps with varying clearance sizes have been examined through adjustment of the geometrical model. Multi-factor analysis of variance is employed to investigate the combined influence of different two-phase flow conditions and tip clearance sizes on the performance of sewage pumps. The results show that the performance of the pump decreases significantly as the clearance size increases. Also, the sensitivity of pump efficiency to variations in tip clearance size is contingent upon the flow rate. Under part-load conditions, both particle concentration and clearance size exhibit a notable effect on efficiency. The two-phase flow will greatly enhance the intensity of the unsteady flow near the inlet and outlet of the semi-open impeller, which is the main reason for the performance degradation of the sewage pump. The findings of this research provide valuable insights for enhancing the hydraulic performance and operational stability of semi-open sewage pumps operating under two-phase flow conditions.

Impact of the Regulation Strategy on the Transient Behavior of a Brayton Heat Pump

High-temperature heat pumps are a key technology for enabling the complete integration of renewables into the power grid. Although these systems may come with several variants, Brayton heat pumps are gaining more and more interest because of the higher heat sink temperatures and the potential to leverage already existing components in the industry. Because these systems utilize renewable electricity to supply high-temperature heat, they are particularly suited for industry or energy storage applications, thus prompting the development of various demonstration plants to evaluate their performance and flexibility. Adapting to varying load conditions and swiftly responding to load adjustments represent crucial aspects for advancing such systems. In this context, this study delves into assessing the transient capabilities of Brayton heat pumps during thermal load management. A transient model of an emerging prototype is presented, comprising thermal and volume dynamics of the components. Furthermore, two reference scenarios are examined to assess the transient performance of the system, namely a thermal load alteration due to an abrupt change in the desired heat sink temperature and, secondly, to a sudden variation in the sink mass flow rate. Finally, two control methodologies—motor/compressor speed variation and fluid inventory control—are analyzed in the latter scenario, and a comparative analysis of their effectiveness is discussed. Results indicate that varying the compressor speed allows for a response time in the 8–20 min range for heat sink temperature regulation (first scenario). However, the regulation time is conditioned by the maximum thermal stress sustained by the heat exchangers. In the latter scenario, regulating the compressor speed shows a faster response time than the inventory control (2–5 min vs. 15 min). However, the inventory approach provides higher COPs in part-load conditions and better stability during the transient phase.

Effects of Varying Equivalence Ratios on the Combustion Efficiency Characteristic of a Dual-Fuel Compression Ignition Engine by Changing Intake Pressures and Exhaust Gas Recirculation Rates

In general, a leaner mixture condition improves combustion efficiency in compression ignition (CI) combustion using diesel. However, in the case of leaner air–fuel mixture conditions, it disturbs flame propagation in spark ignition combustion using gasoline, i.e., low reactivity fuel, causing a decrease in combustion efficiency. Since dual-fuel combustion in a CI engine typically involves the use of high- and low-reactivity fuels together, the differing reactivity conditions in the cylinder become as important as the local equivalence ratio in the cylinder. Thus, there is a need to verify the effect of a leaner mixture condition on combustion efficiency in dual-fuel CI combustion. For this reason, this study experimentally evaluates the effects of varying equivalence ratios on the combustion efficiency of gasoline/diesel dual-fueled CI combustion in a 0.4-L single-cylinder engine under low-speed (1500 rpm) and low-load (total LHV 570 J/str) conditions. To vary the equivalence ratios, intake pressures and exhaust gas recirculation (EGR) rates were, respectively, changed under the part-load condition. The results emphasize that as the equivalence ratio becomes leaner by increasing the intake pressure, combustion efficiency worsens due to the low reactivity properties and certain flame propagation modes of gasoline combustion. On the contrary, increasing the EGR rate did not significantly influence combustion efficiency, but it effectively helped reduce nitrogen oxide (NOx) emissions. Based on these results, it is concluded that optimizing dual-fuel CI combustion to suppress NOx emissions is better achieved using EGR, rather than creating a leaner mixture condition.

Exploring a new criterion to determine the onset of cavitation in centrifugal pumps from energy-saving standpoint; experimental and numerical investigation

This paper proposes a new criterion to determine the cavitation initiation in centrifugal pumps. Because of the importance of saving energy, and the need for specifying a margin for the required net positive suction head (NPSHr) in all centrifugal pumps, a new criterion based on dropping three percent in efficiency (NPSHr,η) was investigated. Extensive experimental and numerical studies were undertaken to assess the effectiveness of the novel criterion from the energy-saving standpoint and its margin compared to the conventional one (NPSHr,Ht). A test bench was employed to conduct numerous experiments on five single-stage centrifugal pumps, generating comprehensive head-drop and efficiency-drop curves under part-load, designed, and over-load conditions. Additionally, simulations were carried out using CFD, employing an appropriate turbulence model and the ZGB cavitation model. Subsequently, dropping curves of total head, hydraulic efficiency, and the torque-rise curve against available NPSH were extracted. Analysis of these simulations revealed that NPSHr,η is consistently higher than NPSHr,Ht. A three-percent total head-drop diminishes the efficiency by an average of 6.04%, ranging from 4.79% to 8.92% depending on the specific case. Using NPSHr,η provides enough distance from the NPSHr,Ht without any need to specify a margin, and a huge amount of energy can be saved annually.

Energy distribution and chaotic pressure pulsation analysis of vortex ropes in Francis-99

Francis turbines, essential for stability in diverse operating conditions and variable-speed scenarios, encounter efficiency-compromising vortex rope formations in the draft tube, leading to substantial pressure fluctuations. This research delves into the analysis of energy loss and pressure fluctuations associated with these vortex ropes. Employing the local entropy generation rate (LEGR) method and chaos theory, we scrutinize the behaviour of vortex ropes and their resultant pressure fluctuations. Notably, vortex ropes exhibit maximum LEGR near the runner cone, with secondary vortices escalating instability downstream. In the elbow section, the collision of vortex ropes with the outer elbow amplifies LEGR, primarily driven by fluctuating velocities (approximately 90%). Leveraging the GWO-VMD algorithm, non-stationary signals are decomposed, unveiling a significant 1.6 Hz vortex rope frequency under partial load (PL) conditions and isolating external noise frequencies, such as the prominent 300 Hz. Following decomposition, chaos theory tools, including phase space reconstruction and phase trajectory graphs, unveil the chaotic nature of PL conditions attributed to spiral vortex ropes, resulting in profound pressure fluctuations. This study enhances our understanding of such systems and provides methodologies for improved noise reduction and optimization of turbine performance.

Modal analysis of vortex rope using dynamic mode decomposition

The decelerating swirling flow in the draft tube of hydraulic turbines at part load conditions often results in a self-induced instability known as vortex rope. This phenomenon is associated with detrimental pressure pulsations in the hydropower system that need to be mitigated. A deep understanding of such instability is essential for developing effective mitigation and control strategies. The current article exploits the dynamic mode decomposition (DMD) algorithm to perform an in-depth modal analysis of the physical aspects of the vortex rope. DMD can efficiently identify distinct coherent structures with isolated frequencies. The sparsity-promoting variant of DMD is exploited to extract the most influential modes. The computational fluid dynamics (CFD) data is generated via a resolved improved delayed detached eddy simulation using OpenFOAM. Frequency analysis of the CFD data uncovered peaks at the normalized frequencies of f/fn=0.56 and 0.63, whose origins seemed initially unclear. Nevertheless, the DMD modal analysis elucidates that these excitations are associated with the rotation of the reunited vortex and fluctuations of the separated boundary layer, respectively. The non-linear dynamics of the flow field are unveiled through a modal decomposition revealing distinctive coherent structures with isolated frequencies. These include rotational and plunging modes of the vortex rope, traveling wakes of the blades, boundary layer separation due to strong adverse pressure gradient, and a reunited vortex core. The flow field reconstruction through time dynamics of DMD modes highlights while it is possible to achieve a perfect flow field reconstruction considering all recovered modes, the model typically fails to predict future behavior with an acceptable level of accuracy. The chaotic nature of the resolved turbulent flow field presents a substantial challenge for predicting the future through a model built based on prior events. The current modal analysis not only provides a more comprehensive understanding of the physics underlying the vortex rope phenomenon but also lays the groundwork for potential future applications in controlling mechanisms.

Optimal flow control of vortex breakdown in a laminar swirling flow

In highly swirling flows, such as hydraulic turbines operating under part-load (PL) conditions, vortex breakdown occurs and performance is impaired. Consequently, it is imperative that mitigation measures are taken. In the present study, a laminar swirling flow with a vortex breakdown at a Reynolds number of 180 is investigated. At the inlet, a swirling velocity profile with a swirl number of 1.095 is set. A stability analysis is conducted to identify unstable modes based on the assumption that vortex breakdown is a global instability. The results indicate that spiral modes with wave number 1 are unstable. An optimal flow control method based on the Adjoint method is then utilized to mitigate vortex breakdown. In the present study, the control method targets vorticity using a minimization algorithm. Control variables include radial and axial body forces. According to the results, the method was effective in mitigating vortex breakdown. A stability analysis conducted during the control process revealed that as the vorticity decreased, the growth-rate of the eigenvalue decreased, indicating that the flow is stabilized.

Multi-condition stability analysis and lightweight research of mining wide-body dump truck compartment

This paper proposes a multi-condition optimization method based on single condition optimization and weight. This method analyzes and discusses various working states of the wide-body dump truck and optimize its structure. Firstly, the modal shape and natural frequency of the carriage under modal conditions are analyzed using the finite element method. Combined with the mechanic’s theory, the carriage’s force, deformation, and stress are studied under the turning and partial load conditions. This part provides a basis for subsequent stability analysis and lightweight research. According to the filtering white noise method and differential equation method, the f-class road model and the vehicle system dynamics model are established in MATLAB to study the influence of road vibration on the stability of the dump truck during operation. The carriage vibration data prove that the road vibration causes the low order resonance of the carriage and affects the stability of the dump truck. This part provides a basis for the subsequent stability optimization. Based on the above analysis, a multi-objective genetic algorithm based on the response surface is used to optimize the structural parameters of the carriage under partial load conditions, turning conditions and modal conditions, to realize the optimization of stability, mass, stress and deformation of the carriage. Finally, the entropy weight method is used to fuse the optimization results of the three working conditions. The correctness of the comprehensive optimization results is verified, and the wide-body dump truck carriage optimization is realized, proving the feasibility of the proposed method.

Investigation of role of fins in a Francis turbine model's cavitation-induced instabilities under design and off-design conditions

Harnessing hydraulic energy for power generation using Francis turbines presents formidable downstream swirl instabilities, which can lead to pressure surges at part load (PL) conditions. Cavitation-induced issues affect not just the PL operations but also the power generation at the best efficiency point (BEP). To combat these challenges, fins strategically placed on the draft tube (DT) periphery aid in low-pressure recovery, which suppresses the hurdles for stable energy extraction. This ongoing study delves deep into the internal flow dynamics of the turbine, considering various Thoma numbers, and evaluating the impact of fins. The investigation employs numerical simulations utilizing structured and unstructured grids, incorporating the Shear Stress Transport (SST) model and the Rayleigh-Plesset model to model turbulent flow in a two-phase mixture. Preliminary findings reveal that at PL, the presence of fins substantially reduces low-pressure zone formation, minimizing vortex ropes and associated instabilities. The fins positively influence axial velocity, reducing swirl intensity and mitigating pressure pulsations by 60 % at PL. Conversely, at the BEP, the impact of fins appears less pronounced, with zero detrimental effect. In conclusion, with no negative effect at BEP, the incorporation of fins enhances the turbine's operational range and ensures smoother and more stable energy production at PL.

Retrofitting Biomass Combined Heat and Power Plant for Biofuel Production—A Detailed Techno-Economic Analysis

Existing combined heat and power plants usually operate on part-load conditions during low heating demand seasons. Similarly, there are boilers designated for winter use that remain inactive for much of the year. This brings a concern about the inefficiency of resource utilization. Retrofitting existing CHP plants (especially for those with spare boilers) for biofuel production could increase revenue and enhance resource efficiency. This study introduces a novel approach that combines biomass gasification and pyrolysis in a polygeneration process that is based on utilizing existing CHP facilities to produce biomethane, bio-oil, and hydrogen. In this work, a detailed analysis was undertaken of retrofitting an existing biomass combined heat and power plant for biofuel production. The biofuel production plant is designed to explore the polygeneration of hydrogen, biomethane, and bio-oil via the integration of gasification, pyrolysis, and renewable-powered electrolysis. An Aspen Plus model of the proposed biofuel production plant is established followed by a performance investigation of the biofuel production plant under various design conditions. An economic analysis is carried out to examine the profitability of the proposed polygeneration system. Results show that the proposed polygeneration system can achieve 40% carbon efficiency with a payback period of 9 years and an internal rate of return of 17.5%, without the integration of renewable hydrogen. When integrated with renewable-power electrolysis, the carbon efficiency could be significantly improved to approximately 90%; however, the high investment cost associated with the electrolyzer system makes this integration economically unfavorable.

Machine Learning-Based Modeling and Predictive Control of Combustion Phasing and Load in a Dual-Fuel Low-Temperature Combustion Engine

<div>Reactivity-controlled compression ignition (RCCI) engine is an innovative dual-fuel strategy, which uses two fuels with different reactivity and physical properties to achieve low-temperature combustion, resulting in reduced emissions of oxides of nitrogen (NO<sub>x</sub>), particulate matter, and improved fuel efficiency at part-load engine operating conditions compared to conventional diesel engines. However, RCCI operation at high loads poses challenges due to the premixed nature of RCCI combustion. Furthermore, precise controls of indicated mean effective pressure (IMEP) and CA50 combustion phasing (crank angle corresponding to 50% of cumulative heat release) are crucial for drivability, fuel conversion efficiency, and combustion stability of an RCCI engine. Real-time manipulation of fuel injection timing and premix ratio (PR) can maintain optimal combustion conditions to track the desired load and combustion phasing while keeping maximum pressure rise rate (MPRR) within acceptable limits.</div> <div>In this study, a model-based controller was developed to track CA50 and IMEP accurately while limiting MPRR below a specified threshold in an RCCI engine. The research workflow involved development of an imitative dynamic RCCI engine model using a data-driven approach, which provided reliable measured state feedback during closed-loop simulations. The model exhibited high prediction accuracy, with an <i>R</i><sup>2</sup> score exceeding 0.91 for all the features of interest. A linear parameter-varying state space (LPV-SS) model based on least squares support vector machines (LS-SVM) was developed and integrated into the model predictive controller (MPC). The controller parameters were optimized using genetic algorithm and closed-loop simulations were performed to assess the MPC’s performance. The results demonstrated the controller’s effectiveness in tracking CA50 and IMEP, with mean average errors (MAE) of 0.89 crank angle degree (CAD) and 46 kPa and Mean absolute percentage error (MAPE) of 9.7% and 7.1%, respectively, while effectively limiting MPRR below of 10 bar/CAD. This comprehensive evaluation showcased the efficacy of the model-based control approach in tracking CA50 and IMEP while constraining MPRR in the dual-fuel engine.</div>

Increase of the Annual Energy Output in Hydraulic Powerplants through Active Flow Control

Traditionally, hydraulic powerplants have been strongly contributing to energy generation. At present, with the expanding participation of other non-storable renewable energy sources in the electrical market composition, water turbines can importantly contribute to the electrical grid stability and to energy storage. With the increasing demand for such services, new procedures have to be developed, in order to allow the hydraulic turbines to operate in critical load conditions, as part load, for example. The technique proposed here, based on pitching guide vanes, was numerically tested with instationary CFD models and delivered possibly promising results, concerning the machine performance and stability, at part load conditions. The extension of the operating range of hydraulic powerplants, through the turbine active flow control, yields even greater flexibility to them in providing regulation services to the electrical grid. This technique has also the potential to extend the operational life of main turbine components and may lead to the increase of the annual energy output in some cases.

Variable evaporating temperature control strategy for a VRF system based on continual estimation of cooling capacity demand of rooms

A variable refrigerant flow system has multiple indoor units for cooling different rooms, and the cooling capacity supply of indoor units depends on evaporating temperature. Existing control strategies of VRF systems generally adopt a constant evaporating temperature which should be low enough to meet the large cooling capacity demand under full load condition, resulting in low energy efficiency. In order to improve energy efficiency, a variable evaporating temperature control strategy is developed, in which evaporating temperature is permitted to rise with the decrease of cooling capacity demand under part load conditions. During the control process, cooling capacity demand of rooms is continually estimated based on indoor thermal balance and room temperature response, and the target evaporating temperature is predicted based on the balance between the cooling capacity supply of indoor units and the cooling capacity demand of rooms. The proposed control strategy has been applied in a VRF system, and its energy efficiency and room temperature variation are tested and compared with those of a same type VRF system that adopts the constant evaporating temperature control strategy. It is shown that the proposed control strategy can improve energy efficiency by 12.6 % and control room temperature fluctuations within ± 0.5 °C.

Impact of impeller blade count on inlet flow pattern and energy characteristics in a mixed-flow pump

Mixed-flow pumps, which amalgamate centrifugal and axial-flow attributes, play a pivotal role in various sectors due to their high efficiency and versatility. This paper, utilizing numerical simulation and experimental validation, addresses the critical role of impeller blade count in mixed-flow pump performance. It investigates the effect of the number of impeller blades on the energy dissipation mechanism and inlet flow pattern of a mixed-flow pump. The results reveal that dynamic and static interference effects, along with the separation vortex due to flow separation, are the main sources of energy dissipation in the pump. Under part-load and part-overload conditions, the increase in the number of blades contributes to the improvement of the flow pattern and performance but may induce more intense rotating stall effects under part-load conditions. In overload conditions, the increase in the number of blades significantly amplifies the volume of the inlet vortex structure, consequently deteriorating the inlet conditions of the impeller. This study provides valuable insights for the design and optimization of mixed-flow pumps.

A Study on Flow Instability in an Axial Compressor of Gas Turbine for Power Generation at Partial-Load Conditions

A Study on Flow Instability in an Axial Compressor of Gas Turbine for Power Generation at Partial-Load Conditions

Downsizing strategy for an air-cooled indirect-fired single-effect ammonia-water absorption chiller in part-load operation in hot climates

A modular mathematical model has been created to simulate an ammonia-water absorption refrigeration system indirectly fired and air-cooled. The model includes governing equations based on mass, species, and energy balances, implemented for the main components of the system. It accounts for both thermal and mass resistances in the transfer processes that occur in the system. The study evaluates the performance of the ROBUR® absorption refrigeration system, model ACF60-00 LB, operating under part-load conditions, driven by hot water temperatures ranging between 160 and 210 °C, while the ambient temperature remains up to 40 °C. This refrigeration system is characterised by including an extra valve that allows active control of the pressure levels of the system. The analysis focusses on the effect of its active control on the size of the system. The results show that increasing the pressure loss in this valve reduces the size of the air-cooled absorber to 37.3 % of its nominal size at an ambient temperature of 40 °C, while the reduction in refrigerant mass flow is 18.5 %, while the condenser size decreases 3.1 times. Evaporator, air-cooled absorber and condenser effectiveness are minimally affected. Additionally, contribution of condenser and evaporator to exergy destruction is balanced.