Determination of the Lumped-Capacitance Parameters of Air-Cooled Servers Through Air Temperature Measurements

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa ◽  
Roger R. Schmidt
Keyword(s):  
Experimental Data ◽  
Air Temperature ◽  
Mathematical Formulation ◽  
Thermal Conductance ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Temperature Measurements ◽  
Inlet Temperature

Computer servers can be represented by lumped thermal capacitances for the purpose of simulating server and data center transient thermal response to changes in operating conditions or equipment failures. Two parameters are needed to characterize the transient behavior of a lumped-capacitance server: its thermal capacitance and its thermal conductance, heat transfer effectiveness, or time constant. To avoid the laborious task of obtaining these parameters from measurements or estimations of the thermal characteristics of internal components of the server, a method is proposed to derive these parameters from external measurements that can be easily obtained without performing an “autopsy” on the server. In this paper, we present the mathematical formulation underlying the proposed method and describe how the parameters are to be obtained from external air-temperature measurements using the mathematical model. We then present validation test cases using experimental data from server shut-down and inlet-temperature ramp tests. The experimentally obtained parameters are implemented into a computational fluid dynamics (CFD) case study of server shutdown in which the transient server exit air temperature is computed from the lumped-capacitance parameters via a user-defined function. The results thus obtained are in excellent agreement with the experimental data.

Transient Thermal Response of Servers Through Air Temperature Measurements

2013 ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa ◽  
Roger R. Schmidt
Keyword(s):  
Thermal Conductance ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Operating Conditions ◽  
Cfd Analysis ◽  
Capacitance Measurements ◽  
Thermal Capacitance ◽  
Transient Thermal ◽  
Transient Thermal Response ◽  
Unsteady Conditions

Transient CFD analysis of data centers requires appropriate representations of the transient thermal characteristics of servers. Thermal conductance and thermal capacitance are two determining characteristics for the response of servers under unsteady conditions. Previous studies proposed tests that require detailed temperature and thermal capacitance measurements for each of the server component, requiring access to individual components inside the server. In this paper, we propose a method for obtaining the transient thermal characteristics of a server from server inlet and outlet temperatures under transient operating conditions.

scholarly journals 2D Numerical Simulation Study of Airfoil Performance

2021 ◽  
Author(s):  
Nasser Shelil
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Air Temperature ◽  
Wind Turbines ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Ansys Fluent

Abstract. The aerodynamic characteristics of DTU-LN221 airfoil is studied. ANSYS Fluent is used to simulate the airfoil performance with seven different turbulence models. The simulation results for the airfoil with different turbulence models are compared with the wind tunnel experimental data performed under the same operating conditions. It is found that there is a good agreement between the computational fluid dynamics (CFD) predicted aerodynamic force coefficients with wind tunnel experimental data especially with angle of attack between −5° to 10°. RSM is chosen to investigate the flow field structure and the surface pressure coefficients under different angle of attack between −5° to 10°. Also the effect of changing air temperature, velocity and turbulence intensity on lift and drag coefficients/forces are examined. The results show that it is recommended to operate the wind turbines airfoil at low air temperature and high velocity to enhance the performance of the wind turbines.

Dynamic Behavior of Plate Heat Exchangers—Experiments and Modeling

1995 ◽  
Vol 117 (4) ◽  
pp. 859-864 ◽  
Author(s):  
S. K. Das ◽  
B. Spang ◽  
W. Roetzel
Keyword(s):  
Theoretical Model ◽  
Dynamic Behavior ◽  
Heat Exchangers ◽  
Dispersion Model ◽  
Flow Direction ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Phase Lag ◽  
Plate Heat

Experiments on the transient behavior of two welded plate heat exchangers with identical construction but different numbers of plates have been carried out under different operating conditions. The temperature response on both sides following a step change in inlet temperature on one side has been compared to a theoretical model. The model takes the effects of flow maldistribution within the channels and between channels into account by introducing a dispersion term in the energy equation. The phase lag due to different flow path lengths between inlet or outlet of the heat exchanger and inlet or outlet of the individual channels are also taken into account. Heat conduction through the plates in the main flow direction of the fluids can be neglected for the exchangers under consideration. The model is validated by the experiments. It is found that the dispersion model considered gives a better simulation than the conventional plug flow model. From the experiments the effects of NTU, heat capacity rate ratio, and number of plates were also determined. This demonstrates the whole spectrum of dynamic behavior of plate heat exchangers. To suggest a proper control strategy for such heat exchangers, the parameters of conventional first and second-order systems with delay period have been determined from the results of the experiments and the theoretical model.

Steady and Transient Behavior of Cross-Flow Three-Fluid Heat Exchanger With Temperature Nonuniformity in All the Fluids—A Detailed Investigation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Harpreet Kaur Aasi ◽  
Manish Mishra
Keyword(s):  
Heat Exchanger ◽  
Cross Flow ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Conditions ◽  
Finite Difference Technique ◽  
Temperature Nonuniformity ◽  
Exit Temperature ◽  
Implicit Finite Difference

Abstract Cross-flow three-fluid plate-fin heat exchanger is analyzed under both steady-state and transient conditions with a nonuniform inlet temperature of all the three fluids. The influence of the longitudinal heat conduction and axial dispersion in the separating sheets and three fluids, respectively, is also considered. Five different combinations (modes) of temperature nonuniformity in the three fluids have been considered and compared for the performance. An important phenomenon of temperature cross between/among the fluids has been observed and presented for certain modes of temperature nonuniformity and operating conditions. The effect in the performance has been presented on the basis of mean exit temperature and deterioration factor. Implicit finite difference technique has been used for the numerical solution. The heat exchanger's performance is found to be dependent on the mode of temperature nonuniformity, number of transfer units, and the operating parameters.

Turbine Inlet Temperature Measurements in a T 8200 kW Gas Turbine Using Water Vapor Emission

2021 ◽  
Author(s):  
Dale R. Tree ◽  
Dustin Badger ◽  
Darrel Zeltner ◽  
Mohsen Rezasoltani
Keyword(s):  
Water Vapor ◽  
Gas Turbine ◽  
Guide Vane ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Test Cell ◽  
Temperature Measurements ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Abstract The measurement of turbine inlet temperature is challenging because of high temperatures and complicated physical access, but continuous measurement of the turbine inlet temperature is very important for maximizing turbine efficiency and increasing durability. This paper provides in-situ turbine rotor inlet temperature (TRIT) measurements in an 8200 kW operating gas turbine engine. The measurements were obtained using integrated spectral infrared (ISIR) emission from the water vapor of the combustion gases entering the turbine rotor. The method utilizes a sapphire optical fiber to convey the signal from the turbine wall to outside the turbine casing. All components are capable of long-term exposure to the turbine operating conditions. The temperature measurements were obtained at 6 operating conditions between 50% and full load. The TRIT temperature was also determined using more than 20 test cell inputs and Solar Turbine’s commercial test cell engine model. The two temperatures (measured and modeled) were within 11 K (less than 1%) across the load sweep. Uncertainty calculations suggest that the uncertainty of the measurement can be expected to be ±2.9% within a confidence interval of 95%. The method also yields the nozzle guide vane surface temperature which was found to increase monotonically with increasing load.

scholarly journals Finding the Thermal Characteristics of a Heat Pipe using Hybrid Nano Fluid

2020 ◽  
Vol 9 (3) ◽  
pp. 597-601
Keyword(s):  
Heat Pipe ◽  
Flow Rate ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Hybrid Nanofluid ◽  
Condenser Section ◽  
Nano Fluid ◽  
Evaporator Section

In this experiment, work was carried out to infer the thermal characteristics of a heat pipe containing nano fluid inside in it. Various Parameters were considered in this experiment, some of them are inlet temperature at one end, mass flow rate (mfr) to evaporator section and inclination angle of heat pipe. In this work three numbers of heat pipes were used and hybrid nanofluid of Al2O3 – TiO2 has been used as cooling fluid in all three heat pipes. The thermal efficiency of the usage of hybrid nanofluidic working system is found to be highest and also this makes the system to get worse in terms of thermal resistance. The flow rate of condenser section was modified to the various ratios from 1:1 to 1:3 as that of evaporator section. To find the thermal characteristics of the heat pipe, many experiments have been carried out by considering many operating conditions. Evaluation on the heat pipe effectiveness was made on basis of gravity assistance to the condenser. The better productiveness of heat pipe when using the hybrid nanofluid has attained when Ch/Cc = 2 and 100 LPH for all operating conditions.

Transient Behavior of a Solid Sensible Heat Thermal Storage Exchanger

1978 ◽  
Vol 100 (1) ◽  
pp. 148-154 ◽  
Author(s):  
J. Szego ◽  
F. W. Schmidt
Keyword(s):  
Heat Storage ◽  
Thermal Response ◽  
Transient Behavior ◽  
Inlet Temperature ◽  
Sensible Heat ◽  
Storage Material ◽  
Storage Unit ◽  
Response Characteristics ◽  
Rectangular Channels ◽  
Heat Storage Material

The transient response characteristics of a solid sensible heat storage exchanger which interacts with two energy transporting fluids are presented. The storage unit is composed of a series of large aspect ratio rectangular channels for the fluids, separated by slabs of the heat storage material. The hot and cold fluids flow in counter current fashion, in alternate channels so that each slab of storage material is in contact with both fluids. The entire system is considered to be initially in equilibrium at a uniform temperature, a step change in the inlet temperature of one of the fluids is imposed, and the thermal response of the unit is predicted until steady state conditions are reached. The response of the storage exchanger to an arbitrary time variation of one of the fluids’ inlet temperature may be obtained using superposition.

Computational and Experimental Investigation of Emissions in a Highly Humidified Premixed Flame

2003 ◽  
Author(s):  
Fredrik Hermann ◽  
Jens Klingmann ◽  
Rolf Gabrielsson
Keyword(s):  
Air Temperature ◽  
Combustion Efficiency ◽  
Reaction Scheme ◽  
Operating Conditions ◽  
Aerodynamic Load ◽  
Inlet Temperature ◽  
Atmospheric Conditions ◽  
Air Inlet ◽  
Stirred Reactor ◽  
Maximum Humidity

Emission formation and flame stability were investigated, both experimentally and computationally, for premixed combustion with varying amounts of water vapor in the mixture. Emission measurements were made in a gas turbine combustor at atmospheric conditions, using Danish Natural Gas (NG) as fuel. The emissions were mapped as a function of humidity, inlet air temperature, equivalence ratio and aerodynamic load. Operating conditions were chosen to match what can be expected from e.g. an EvGT cycle for power generation. The inlet air temperature was slightly lower than the inlet temperatures that would be found in a recuperated cycle. The degree of humidity was varied from 0w% to 33w% of the airflow in the experiment, while the air inlet temperature was varied from 500K to 800K. Computations were made using a single Perfectly Stirred Reactor (PSR) model and a reaction scheme with 821 reactions and 69 species. It was found that the NOx emissions were strongly reduced by the addition of water. Most of this decrease vanishes in practical combustion since richer combustion is required to keep CO emissions (combustion efficiency) at a tolerable level. The maximum humidity was found to be dependent on inlet air temperature and aerodynamic load. In this experiment, the maximum humidity achieved was 33%.

Turbine Inlet Temperature Measurements in A T 8200 KW Gas Turbine Using Water Vapor Emission

2021 ◽  
Author(s):  
Dale Tree ◽  
Dustin Badger ◽  
Darrel Zeltner ◽  
Mohsen Rezasoltani
Keyword(s):  
Water Vapor ◽  
Gas Turbine ◽  
Guide Vane ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Test Cell ◽  
Temperature Measurements ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Abstract The measurement of turbine inlet temperature is challenging because of high temperatures and complicated physical access, but continuous measurement of the turbine inlet temperature is very important for maximizing turbine efficiency and increasing durability. This paper provides in-situ turbine rotor inlet temperature (TRIT) measurements in an 8200 kW operating gas turbine engine. The measurements were obtained using integrated spectral infrared (ISIR) emission from the water vapor of the combustion gases entering the turbine rotor. The method utilizes a sapphire optical fiber to convey the signal from the turbine wall to outside the turbine casing. All components are capable of long-term exposure to the turbine operating conditions. The temperature measurements were obtained at 6 operating conditions between 50% and full load. The TRIT temperature was also determined using more than 20 test cell inputs and Solar Turbine's commercial test cell engine model. The two temperatures (measured and modeled) were within 11 K (less than 1%) across the load sweep. Uncertainty calculations suggest that the uncertainty of the measurement can be expected to be ±2.9% within a confidence interval of 95%. The method also yields the nozzle guide vane surface temperature which was found to increase monotonically with increasing load.

Numerical Simulation of the Effects of a Thermally Significant Blood Vessel on Freezing by a Circular Surface Cryosurgical Probe Compared With Experimental Data

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Genady Beckerman ◽  
Avraham Shitzer ◽  
David Degani
Keyword(s):  
Experimental Data ◽  
Blood Vessel ◽  
Cooling Rate ◽  
Flow Rate ◽  
Freezing Point ◽  
Cylindrical Tube ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Cooling Rates ◽  
Flow Rates

The dynamic thermal interaction between a surface cryosurgical probe (heat sink) and an embedded cylindrical tube (heat source), simulating a thermally-significant blood vessel, has been studied. The cryoprobe was operated by liquid nitrogen while the embedded tube was perfused by water at a constant inlet temperature. Previous experimental data were obtained in a phase-changing medium (PCM) made of 30%/70% by volume mashed potato flakes/distilled-water solution. A parametric study was conducted without the embedded tube, and with flow rates of 30 ml/min and 100 ml/min in the tube, while cooling rates at the tip of the cryoprobe were maintained at −4°C/min, −8°C/min, or −12°C/min. Numerical thermal analysis was performed by ANSYS7.0 and showed good conformity to the experimental data. The results quantify the effects of these parameters on both the shape and extent of freezing obtained in the PCM. For 20 min of operation of the cryoprobe, water temperatures inside the tube remained well above the freezing point for all assumed operating conditions. Frozen volumes of the 0°C isotherm, approximating the “frozen front,” and the −40°C isotherm, representing the “lethal temperature,” were smallest for the combination of highest cooling rate at the cryoprobe and the highest flow rate in the tube, (−12°C/min and 100 ml/min). The results indicate that both the flow rates in the embedded tube, and the cooling rates applied at the cryoprobe, have similar qualitative effects on the size of the PCM frozen volumes; increasing either one will cause these volumes to decrease. Under the conditions of this study the effects of flow rate in the tube are more pronounced, however, effecting relative frozen volumes decreases by about 10–20% while those of the cooling rate at the cryoprobe are in the range of 7–14%.

Sign in / Sign up

Export Citation Format

Share Document