Performance analysis of a novel ejector-assisted condenser outlet split dual-evaporator refrigeration system

Sachdeva Gulshan,Anuradha Parinam,Jain Vaibhav,VenkataTeja Y. T. 대한설비공학회 2024 International Journal of Air-Conditioning and Refr Vol.32 No.1

The performance of an ejector-assisted condenser outlet split dual-evaporator cycle is compared with a conventional dual-evaporator cycle albeit consisting a pressure reducing valve. The cycles do not employ any separator due to its inability to efficiently separate the liquid and the vapor phases. The comparison of both the cycles has been made for the same cooling capacity in low-temperature evaporator and unit flow rate of R134a and R1234yf as refrigerants. The impacts of changing the operating temperatures of evaporator and condenser have been examined in the current investigation. The study reveals that with the increase in temperature of the high-temperature evaporator, the cooling capacity of the high-temperature evaporator yields, while that of the low-temperature evaporator plummets in both the cycles. Further, the compressor work is allayed in the ejector-assisted cycle; thus, the COP is enhanced considerably. The percentage COP improvement over the basic cycle is obtained from 14.7 to 17.53% for the refrigerant R1234yf and from 14.45 to 17.32% for R134a; however, the COP of both the cycles with R12134yf is slightly lower than with R134a. The ejector has been modeled assuming a constant pressure theory. The observed trend indicates that the entrainment ratio is improved with the rise in the temperature of low-temperature evaporator, whereas it is decreased with the rise in the temperature of high-temperature evaporator.

Performance evaluation of different shapes of headed bars in steel fiber reinforced concrete

Sachdeva, Payal,Danie Roy, A.B.,Kwatra, Naveen Techno-Press 2021 Advances in concrete construction Vol.11 No.5

The behavior of headed bars in concrete is investigated through 108 pullout tests having an embedment depth of eight times the bar diameter in the M20 concrete mix. Headed bars are designed based on ASTM A970-16 and ACI 318-19 recommendations. The primary parameters used in this study are the steel bar diameter, the steel fibers percentage, and the head shapes. Three failure modes namely, Steel, Concrete-Blowout & Pull-Through failure have been observed. Based on load-deflection curves which are plotted to investigate the bond capacity of headed bars, it is observed that the circular-headed bars have displayed the highest peak load. The comparative analysis shows the smaller differences in the ultimate bond strength between MC2010 (0.89-2.26 MPa) and EN 1992-1-1 (2.32 MPa) as compared to ACI-318-19 (11-22 MPa) which is due to the absence of embedment depth and peak load factor in MC2010 and EN 1992-1-1 respectively.

Exergy Analysis of an Ejector Cooling System by Modified Gouy–Stodola Equation

Sachdeva Gulshan,Sharma Bharat 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.3

In this paper, exergy destruction analysis of a heat-assisted ejector cooling system has been carried out using a modified Gouy–Stodola equation. The modified Gouy–Stodola equation provides a more accurate and realistic irreversibility analysis of the system than the conventional Gouy–Stodola formulation. The coefficient of structural bond (CSB) analysis has also been executed to find the component whose operating variables affect the system’s total irreversibility at the most. Exergy analysis revealed that the maximum exergy loss happens in the ejector followed by the generator and condenser. The model predicted 40.84% of total irreversibility in the ejector at the designed conditions. However, total exergy destruction is found to be the most sensitive to the evaporator temperature. The CSB value of 12.97 is obtained in the evaporator using the modified exergy method. The generator appears to be the second sensitive component with the CSB value of 2.42, followed by the condenser with the CSB value of 1.628. The coefficient of performance of the system is found to be 0.18 at the designed conditions. The refrigerant R1234yf is considered in the system.

Totally Umbilical Slant Lightlike Submanifolds of Indefinite Kaehler Manifolds

Sachdeva, Rashmi,Kumar, Rakesh,Bhatia, Satvinder Singh Department of Mathematics 2017 Kyungpook mathematical journal Vol.57 No.3

In this paper, we study totally umbilical slant lightlike submanifolds of indefinite Kaehler manifolds. We prove that there do not exist totally umbilical proper slant lightlike submanifolds in indefinite Kaehler manifolds other than totally geodesic proper slant lightlike submanifolds. We also prove that there do not exist totally umbilical proper slant lightlike submanifolds of indefinite Kaehler space forms. Finally, we give a characterization theorem on minimal slant lightlike submanifolds.

Comparative performance investigation of a dual evaporator cycle using an ejector with the conventional cycle using a pressure reducing valve

Sachdeva Gulshan,Jaiswar Ajay,Anuradha Parinam,Jain Vaibhav 대한설비공학회 2023 International Journal of Air-Conditioning and Refr Vol.31 No.1

The performance of a dual evaporator cycle using ejector is compared with a conventional cycle employing pressure reducing valve. In both the systems, high temperature evaporator is considered as a flooded evaporator, thus a separator is employed after the high temperature evaporator. However, low temperature evaporator is a kind of conventional dry evaporator. The comparison of both systems, i.e., conventional and ejector assisted, is done for the same cooling capacities and same dryness fraction at the exit of high temperature evaporator with R134a, R152a, and R1234yf refrigerants. The effects of varying the states of refrigerant at the exit of flooded evaporator, and temperatures of both the evaporators and the condenser are analyzed using Engineering Equation Solver. It is found that the compressor work is reduced in both the cycles with the rise in low temperature evaporator temperature; however, a little variation is observed in the total cooling effect. The cooling effect in high temperature evaporator is increased with the increase in dryness fraction at the exit of the high temperature flooded evaporator, but it is decreased in low temperature evaporator.

Energy Analysis of a Vapor Compression System Cascaded with Ammonia-Water Absorption System

GULSHAN SACHDEVA,VAIBHAV JAIN,S. S. KACHHWAHA 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.1

The first law analysis of a vapor compression–vapor absorption (VC–VA) cascade system iscarried out for a wide range of cooling capacity. While ammonia–water is the working pair in VAsection, R407C is used in VC section. The in°uences of change in cooling capacity, superheatingand subcooling in the condenser, temperature in the generator, degree of overlap in cascadecondenser, size of the heat exchangers etc. on the system performance are investigated. It isconcluded that the COP of the VC section of the cascade system could be improved by 146% andthe electricity consumption could be reduced by 64% compared to an equivalent VC unit. Separately the results showed the considerable increase in the generator heat when coolingcapacity was increased from 83.33kW. The COP of the cascade system at high cooling capacity isstrongly dependent on the performance of condenser.

Interferon-gamma release assay has poor diagnostic accuracy in differentiating intestinal tuberculosis from Crohn’s disease in tuberculosis endemic areas

Karan Sachdeva,Peeyush Kumar,Bhaskar Kante,Sudheer K. Vuyyuru,Srikant Mohta,Mukesh K. Ranjan,Mukesh K. Singh,Mahak Verma,Govind Makharia,Saurabh Kedia,Vineet Ahuja 대한장연구학회 2023 Intestinal Research Vol.21 No.2

Background/Aims: Intestinal tuberculosis (ITB) and Crohn’s disease (CD) frequently present with a diagnostic dilemma because of similar presentation. Interferon-gamma release assay (IGRA) has been used in differentiating ITB from CD, but with sparse reports on its diagnostic accuracy in tuberculosis endemic regions and this study evaluated the same. Methods: Patients with definitive diagnosis of ITB (n=59) or CD (n=49) who underwent IGRA testing (n=307) were retrospectively included at All India Institute of Medical Sciences, New Delhi (July 2014 to September 2021). CD or ITB was diagnosed as per standard criteria. IGRA was considered positive at >0.35 IU/mL. Relevant data was collected and IGRA results were compared between ITB and CD to determine its accuracy. Results: Among 59 ITB patients (mean age, 32.6±13.1 years; median disease duration, 1 year; male, 59.3%), 24 were positive and 35 tested negative for IGRA. Among 49 CD patients (mean age, 37.8±14.0; median disease duration, 4 years; male, 61.2%), 12 were positive and 37 tested negative for IGRA. Hence, for diagnosing ITB, IGRA showed a sensitivity, specificity, positive and negative predictive values of 40.68%, 75.51%, 66.67%, and 51.39%, respectively. The area under the curve of IGRA for ITB diagnosis was 0.66 (95% confidence interval, 0.55–0.75). In a subset (n=64), tuberculin skin test (TST) showed sensitivity, specificity, positive and negative predictive values of 64.7%, 73.3%, 73.3%, and 64.71%, respectively. IGRA and TST were concordant in 38 (59.4%) patients with κ=0.17. Conclusions: In a tuberculosis endemic region, IGRA had poor diagnostic accuracy for differentiating ITB from CD, suggesting a limited value of IGRA in this setting.

Performance improvements of organic solar cell using dual cathode buffer layers

Sheenam Sachdeva,Jagdish Kaur,Kriti Sharma,S.K. Tripathi 한국물리학회 2018 Current Applied Physics Vol.18 No.12

The present study deals with the effect of dual cathode buffer layer (CBL) on the performance of bilayer of 4,4′- cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) and fullerene (C70)-based organic solar cell (OSC) with low donor concentration. OSC devices with CBLs have been fabricated using thermal vapor deposition technique. We report the use of lithium fluoride (LiF) and molybdenum trioxide (MoO3) as CBLs. The insertion of LiF between C70 and aluminium (Al) electrode enhances the power conversion efficiency (PCE) of device from 1.89% to 2.47% but quenching of photogenerated excitons is observed at interface of C70 and LiF layers. Incorporation of MoO3 between LiF and Al electrode further enhances PCE of device to 3.51%. This has also improved the material quality and device properties, by preventing the formation of gap states and diminishing exciton quenching.

Effect of calcium addition on microstructure and electrical properties of lead zirconate titanate ceramic compositions near MPB

Anupama Sachdeva,Aarushib,Jagneet Kaur Anand,R. P. Tandon 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.1

Calcium modified lead zirconate titanate ceramic compositions Pb(1-x)CaxZr0.52Ti0.48O3, where x=0, 0.02, 0.04, 0.06, 0.08, 0.1,have been prepared by solid state reaction method using wet milling. Scanning Electron Microscopy (SEM) studies have beencarried out to see the variation in the grain size with calcium addition. A correlation of the dielectric constant and dielectricloss with grain size effect is presented in this paper. A monotonic decrease in the transition temperature along with morediffuseness in paraelectric-ferroelectric phase transition is observed with increasing calcium content. The values of activationenergy (Ea) for the samples, calculated for ferroelectric region near phase transition temperature, are found to be in the rangeof approximately 0.6-1.0 eV which reflects that the main charge carriers responsible for conduction at higher temperaturesare oxygen ion vacancies.

EXERGY ANALYSIS OF A VAPOR COMPRESSION–VAPOR ABSORPTION CASCADE SYSTEM

GULSHAN SACHDEVA,VAIBHAV JAIN,S. S. KACHHWAHA 대한설비공학회 2013 International Journal of Air-Conditioning and Refr Vol.21 No.4

In this paper, second law analysis has been done for the vapor compression–vapor absorption (VC–VA) cascade system. Ammonia–water is considered as the working pair in absorption section and R407C is dealt as the working °uid in VC section. Exergy destruction or the irreversibility rate is determined in each components of VC–VA cascade system, for a wide range of cooling capacity by considering a variable speed reciprocating compressor. Further in this, Coe±cient of structural bond (CSB) analysis is carried out to quantify the effect of varying the generator temperature, effectiveness of solution heat exchanger, inlet temperature of external °uids in evaporator/condenser and some other variables. Solution heat exchanger and the condenser are reported to have high CSB value, so have a great scope of improvement to reduce the irreversibility rate of the whole system.