The Effect of Cooling Rate on the Formation of Dendritic Ice in a Pipe With No Main Flow

1977 ◽  
Vol 99 (3) ◽  
pp. 419-424 ◽  
Author(s):  
R. R. Gilpin
Keyword(s):  
Temperature Distribution ◽  
Cooling Rate ◽  
Dendritic Growth ◽  
Pipe Wall ◽  
Ice Nucleation ◽  
Thermal Boundary Condition ◽  
Main Flow ◽  
Freezing Process ◽  
Water Pipe ◽  
Flow Through

Dendritic ice forms in a pipe when there is no main flow through the pipe during the freezing process. This ice form occurs because the quiescent water supercools considerably below 0°C before ice nucleation occurs. It has been shown that growth of dendritic ice can cause blockage of a water pipe [1] much sooner than would have been predicted if the ice grew as a solid annulus. The extent of the dendritic growth is largely determined by the temperature distribution that exists in the pipe at the time of ice nucleation. In this paper the factors effecting the temperature distribution and thus the extent of dendritic ice growth are examined to determine the conditions under which blockage by dendritic ice is likely to occur. The factors that are important are the cooling rate the pipe is exposed to, the ice nucleation temperature, and the type of thermal boundary condition the pipe wall provides.

scholarly journals Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

2015 ◽  
Vol 15 (9) ◽  
pp. 13109-13166
Author(s):  
P. A. Alpert ◽  
D. A. Knopf
Keyword(s):  
Cooling Rate ◽  
Surface Area ◽  
Ice Nucleation ◽  
Rate Dependence ◽  
Nucleation Theory ◽  
Freezing Process ◽  
Nucleation Kinetics ◽  
Rate Dependent ◽  
Immersion Freezing ◽  
The Impact

Abstract. Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An apparent cooling rate dependence ofJhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. In an idealized cloud parcel model applying variability in ISAs for each droplet, the model predicts enhanced immersion freezing temperatures and greater ice crystal production compared to a case when ISAs are uniform in each droplet. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

scholarly journals Numeric modeling of a micro-scale differential thermal calorimeter for the purpose of cryopreservation

2017 ◽  
Author(s):  
◽  
Han Han
Keyword(s):  
Heat Flux ◽  
Temperature Distribution ◽  
Cooling Rate ◽  
Water Droplet ◽  
Biological Material ◽  
Computational Time ◽  
Freezing Process ◽  
Water Droplets ◽  
Micro Scale ◽  
Numeric Model

Cryopreservation requires biological material to be stored at temperatures well below the freezing point of water. During the process of cryopreservation, the cooling rate should be carefully chosen to avoid cell damage due to the unbalanced pressure and the solution effect. Cellular thermal analysis that determines the thermodynamics properties of a micro-scale biological material is necessary for a successful cryopreservation procedure. A micro-scale differential thermal analyzer (uDTA) was previously developed to obtain accurate thermal properties measurements of freezing cells. However, the thermal signal needs to be properly interpreted in terms of how much ice is created. Also, the future cooling profile needed to experimentally control the cooling rate needs to be developed. So a 3D numeric model was built in STAR CCM+ to study the temperature change of the water droplets while being frozen by a thermoelectric module. The heat flux profile for the boundary condition was scaled to accommodate the heat spread effect. The numeric model solutions successfully matched the temperature distribution results from the experiments. By using additional heat flux to accommodate the heat spread effect, the STAR CCM+ model generated relatively accurate results on a smaller geometry within a very short computational time. This is a big improvement compared with other high fidelity computational simulation models used to solve similar problems. After the 3D model was calibrated, the same STAR CCM+ model was used to predict the temperature distribution of different sizes of water droplets during the freezing process. This model allowed us to better understand the temperature distribution of a water droplet when the water droplet was being cooled until frozen. The modeling technique developed in this research will help establish the required cooling rates needed to control ice formation and establish thermodynamic properties of cell freezing solutions.

scholarly journals Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

2016 ◽  
Vol 16 (4) ◽  
pp. 2083-2107 ◽  
Author(s):  
Peter A. Alpert ◽  
Daniel A. Knopf
Keyword(s):  
Experimental Data ◽  
Cooling Rate ◽  
Surface Area ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Freezing Process ◽  
Nucleation Kinetics ◽  
Rate Dependent ◽  
Immersion Freezing

Abstract. Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous-flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time-dependent isothermal frozen fractions exhibiting non-exponential behavior can be readily explained by this model considering varying ISA. An apparent cooling-rate dependence of Jhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling-rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

Controlled Freezing of Nonideal Solutions With Application to Cryosurgical Processes

1991 ◽  
Vol 113 (4) ◽  
pp. 430-437 ◽  
Author(s):  
H. M. Budman ◽  
J. Dayan ◽  
A. Shitzer
Keyword(s):  
Cooling Rate ◽  
Freezing Process ◽  
Data Sets ◽  
Tracking Accuracy ◽  
Loop Control ◽  
Set Point ◽  
New Device ◽  
Loop Control System ◽  
The Stability ◽  
Controlled Freezing

Success of a cryosurgical procedure, i.e., maximal cell destruction, requires that the cooling rate be controlled during the freezing process. Standard cryosurgical devices are not usually designed to perform the required controlled process. In this study, a new cryosurgical device was developed which facilitates the achievement of a specified cooling rate during freezing by accurately controlling the probe temperature variation with time. The new device has been experimentally tested by applying it to an aqueous solution of mashed potatoes. The temperature field in the freezing medium, whose thermal properties are similar to those of biological tissue, was measured. The cryoprobe temperature was controlled according to a desired time varying profile which was assumed to maximize necrosis. The tracking accuracy and the stability of the closed loop control system were investigated. It was found that for most of the time the tracking accuracy was excellent and the error between the measured probe temperature and the desired set point is within ±0.4°C. However, noticeable deviations from the set point occurred due to the supercooling phenomenon or due to the instability of the liquid nitrogen boiling regime in the cryoprobe. The experimental results were compared to those obtained by a finite elements program and very good agreement was obtained. The deviation between the two data sets seems to be mainly due to errors in positioning of the thermocouple junctions in the medium.

scholarly journals Flow through a plane orifice in a pipe wall

1965 ◽  
pp. 143-148
Author(s):  
J. A. SANDOVER ◽  
J. A. TALLIS
Keyword(s):  
Pipe Wall ◽  
Flow Through

scholarly journals Finite Element Analysis of Temperature Distribution and Stress Behavior of Squeeze Pressure Composites

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
P. Gurusamy ◽  
T. Sathish ◽  
V. Mohanavel ◽  
Alagar Karthick ◽  
M. Ravichandran ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Cooling Rate ◽  
Base Alloy ◽  
Cast Alloy ◽  
Simulation Software ◽  
Engineering Industry ◽  
Effect Of Temperature ◽  
Cooling Curves ◽  
Squeeze Pressure

Aluminium-reinforced composites play a vital role in the engineering industry because of their better strength and stiffness. The properties are directly related to the solidification phenomenon of the cast alloy. The design engineer should understand the importance of the solidification behavior of base alloy and its reinforcement. Composites’ solidification study is rare, and the reviews are limited. The solidification process is analyzed using the finite element method (FEM), and this would fetch a lot of information about the cooling rate of the composites and also helps to reduce the time in experimentation. This paper reports and plots the cooling curves of Al/SiCp composites using simulation software. Cylindrical-shaped composites were developed using the squeeze casting method, and the experimental cooling curves were plotted using a K-type thermocouple. Composites samples were prepared at the following squeeze pressures: 0, 30, 50, 70, 100, and 130 MPa; melt and die temperature was kept constant at 800 and 400°C, respectively. The experimental and FEA cooling curves were compared, and it was agreed that the increase in the squeeze pressure increases the cooling rate of the developed composite. Furthermore, the effect of temperature distribution from the inner region of the melt and die material which causes the radial and tangential stress of components has also been examined.

Effect of Controlled Ice Nucleation on Primary Drying Stage and Protein Recovery in Vials Cooled in a Modified Freeze-Dryer

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Stéphanie Passot ◽  
Ioan Cristian Tréléa ◽  
Michèle Marin ◽  
Miquel Galan ◽  
G. John Morris ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Nucleating Agent ◽  
Ice Nucleation ◽  
Residual Water ◽  
Activity Recovery ◽  
Protective Medium ◽  
Ultrasound Technology ◽  
Controlled Nucleation ◽  
The Impact ◽  
Freeze Dryer

The freezing step influences lyophilization efficiency and protein stability. The main objective of this work was to investigate the impact on the primary drying stage of an ultrasound controlled ice nucleation technology, compared with usual freezing protocols. Lyophilization cycles involving different freezing protocols (applying a constant shelf cooling rate of 1°C/min or 0.2°C/min, putting vials on a precooled shelf, and controlling nucleation by ultrasounds or by addition of a nucleating agent) were performed in a prototype freeze-dryer. Three protective media including sucrose or maltodextrin and differing by their thermal properties and their ability to preserve a model protein (catalase) were used. The visual aspect of the lyophilized cake, residual water content, and enzymatic activity recovery of catalase were assessed after each lyophilization cycle and after 1 month of storage of the lyophilized product at 4°C and 25°C. The freezing protocols allowing increasing nucleation temperature (precooled shelf and controlled nucleation by using ultrasounds or a nucleating agent) induced a faster sublimation step and higher sublimation rate homogeneity. Whatever the composition of the protective medium, applying the ultrasound technology made it possible to decrease the sublimation time by 14%, compared with the freezing method involving a constant shelf cooling rate of 1°C/min. Concerning the enzyme activity recovery, the impact of the freezing protocol was observed only for the protective medium involving maltodextrin, a less effective protective agent than sucrose. Higher activity recovery results were obtained after storage when the ultrasound technology or the precooled shelf method was applied. Controlling ice nucleation during the freezing step of the lyophilization process improved the homogeneity of the sublimation rates, which will, in turn, reduce the intervial heterogeneity. The freeze-dryer prototype including the system of controlled nucleation by ultrasounds appears to be a promising tool in accelerating sublimation and improving intrabatch homogeneity.

scholarly journals Comparison of numerical and experimental results of water -pipe wall interaction

2015 ◽  
Vol 4 (2) ◽  
pp. 277
Author(s):  
Ali Heidari ◽  
Poria Ghassemi
Keyword(s):  
Network Flow ◽  
Pipe Wall ◽  
Tube Wall ◽  
Pressure Change ◽  
Fluid Distribution ◽  
Water Pipe ◽  
Pipe System ◽  
Steel Bar ◽  
Wall Interaction ◽  
Different Parts

Tube wall analysis on unsteady network flow of pipe shows that the column is separated when it reached to vapor pressure. In this study, we experiment dynamic behavior of fluid distribution pipe system. The model used in is a straight suspended pipe, which is striked by a solid steel bar. Then the results of pressure change in different parts of pipe has been studied and compared with valid results.  

Sign in / Sign up

Export Citation Format

Share Document