Large Temperature Drop Research Articles

Analysis of the Effect of Central Gap Size on the Temperature Profile and Fissile Content in the Annular Nuclear Fuel Rod

The perturbation in temperature profile and fissile content due to variation in the central gap of an isolated annular cylindrical fuel rod of a pressurized water reactor was studied by analytical calculation. Four different models namely UO2+Zircaloy-4+He, UO2+ Zr-1%Nb +He, MOX+Zircaloy-4+He, and MOX+ Zr-1%Nb +He were considered. The radial temperature profile was generated for different ratios (α) of outer to inner fuel radius. Lower fuel temperature was observed for small values of α and vice versa. The peak fuel temperature and temperature drop across the fuel pellets were calculated. Models of MOX fuel showed higher peak fuel temperature and large temperature drop than the models of UO2 for the same fuel cladding. Zr-1%Nb cladding results in a slightly higher fuel temperature than Zircaloy-4 for the same fuel composition. The faster changes of these parameters with α were found for UO2 than MOX fuel. The change in fissile loading with α was also studied and a sharp increase is observed if exceeds α=2.50. DUJASE Vol. 6 (2) 72-76, 2021 (July)

On the rupture of bubble foam in subcooled flow boiling of seawater in a vertical annulus

This paper investigates the nature of foam rupture and its effects on heat transfer during subcooled flow boiling of 3.5 wt% artificial seawater in a vertical annulus. Flow visualizations near the outlet of the heated section using a high-speed camera disclose the rupture of foam flow and the following development of slug bubble for the inlet temperatures of 55°C, 65°C, and 75°C and boiling numbers ranging from 3 × 10−4 to 11 × 10−4. The slug flow, otherwise, is absent for the case with inlet temperature of 85°C in this study and 90°C, as reported in our previous study. The nature of such foam rupture and evolution of slug flow is studied through the image processing and measurements in Image J. Geometric characteristics including the Feret diameters, equivalent diameters, angles, and aspect ratios are measured and discussed. Motion characteristics including the bubble growth rates, velocities and trajectories of slug bubbles are also measured and analyzed. It reveals that the slug bubble grows approximately linearly. However, the bubble growth rate demonstrates large variations and crucial effect on heat transfer. The trajectories of the slug bubbles reveal zigzag motions with large radial displacements. A theory is proposed to explain the ruptures of bubble foam. Such coexistence of foam flow and slug flow enhances significantly heat transfer in subcooled flow boiling, leading to a large wall temperature drop up to 10°C, compared with 1°C in those cases with stable foam flow in artificial seawater and slug flow in de-ionized water.

A new on-line ultrasonic thickness monitoring system for high temperature pipes

On-line thickness monitoring of pipe wall is very important in petrochemical and power generation industries. There are two main reasons that the conventional ultrasonic transducers cannot withstand long-term on-line monitoring in high temperature. One is that the piezoelectric elements within transducers depolarize causes them to fail, the other is that the working medium inside the pipeline interferes with the ultrasonic wave results in the decline of measurement accuracy. In order to overcome these problems, an ultrasonic thickness gauge using a waveguide that can sustain a large temperature drop and effectively transmit the quasi-fundamental shear horizontal (SH0*) wave without causing dispersion is designed. The waveguide can isolate the vulnerable piezoelectric sensor from the high-temperature measurement zone, and the SH0* wave can avoid interfere of the working medium. Moreover, a monitoring system applying this ultrasonic thickness gauge is discussed and the application method of this system is introduced. The high temperature long-term reliability experiments carried out both in laboratory and on-site, and wall thinning measurement by corrosion experiments show that the designed thickness gauge has good accuracy and long-term stability, which can meet the needs of long-term on-line monitoring of high temperature pipes.

Performance assessment of annular thermoelectric generators for automobile exhaust waste heat recovery

Annular thermoelectric generators (ATEGs), matched well with the exhaust pipe in geometry, are proposed to recover the heat from automobiles. A theoretical model was constructed to assess the performance of automotive exhaust ATEGs (AEATEGs), where a finite element method was used to incorporate the temperature variation and temperature-dependent properties. The local pressure drop as to the change of cross-section area and shape was considered. Performance comparison with commonly used automotive exhaust flat-plate thermoelectric generators (AEFTEGs) was conducted. Also, the effects of flow arrangement and operating parameters were clarified. Results show that the performance of AEATEGs outperforms AEFTEGs, with the net power on average 1.1% higher. With increasing cooling medium flow rate, the net power increases until attaining a maximum and decreases afterwards. A flow rate of 0.05 kg/s is preferred for the compromise of coolant temperature rise and tank volume. In light of a large temperature drop from exhaust to generators, a simple strategy, inserting a hollow cylinder into heat exchanger, was developed and its effectiveness was evaluated. The maximum enhancement in net power of 214.0% is exhibited, but which reduces notably with increasing exhaust flow rate. For gasoline automobiles, a cylinder with dimensionless diameter of 0.8 is recommended.

SOx removal and emission characteristics of WFGD system applied in ultra-low emission coal-fired power plants

In this paper, SOX (SO2 and SO3) removal and emission characteristics of wet limestone-gypsum flue gas desulfurization (WFGD) are investigated based on the data collected from 95 ultra-low emission coal-fired power units. The study shows that the overall removal efficiency of single-absorber is above 97.5%, in which the SO3 removal efficiency is between 31% and 70%. When the inner structures are installed into the spray absorber, the correlation between the inlet SO2 concentration and SOX removal efficiency becomes more obvious, however, with a tray absorber, the maximum SO2 removal efficiency of double-absorber reaches 99.74%, in which the SO3 removal efficiency is between 27% and 81%. With a normal spray absorber, the higher inlet concentration, the higher removal efficiency it reaches, while with a tray absorber, the result is opposite. With a single-absorber, there is little correlation between flue gas temperature drop and SO2 removal efficiency. Large temperature drop harms the improvement of overall SO2 removal efficiency but is beneficial to SO3 removal. By the calculation of SOX emission performance model, average emission performances of SO2 and SO3 are acquired, which are about 90–107 mg/(kW·h) and 81–97 mg/(kW·h), respectively.

Resistance investigation of diamond-like carbon coatings to cyclic temperature changes

Optical elements used in outer space must be designed considering the effects of such factors as space vacuum, atomic oxygen in low Earth orbit, solar and space radiation, large temperature drops, gas release of spacecraft materials and structural elements, space dust and debris. In order to harden and protect mirror surfaces of optical elements from external factors, it has been promisingly applied diamond-like carbon coatings on their surface. These coatings are characterized by high strength and wear-resistant properties, in particular, high hardness, low friction coefficient, high wear resistance and chemical inertness. This leads to their widespread use in various fields of science and technology, including optical instrumentation. This paper presents the results of testing an aluminum mirror with a diamondlike carbon coating under the effect of cyclic temperature changes for determining their ability to withstand a rapid cyclic ambient temperature change, and specifically, to maintain optical and mechanical properties.

Effects of temperature rising inhibitor and shrinkage reducing admixture on pore structure of early-age cement paste

High-strength and high-performance concrete (HSHPC) is frequently used in practical engineering, but HSHPC tends to crack at an early age because of the large temperature drop (temperature shrinkage) and autogenous contraction. Therefore, a temperature rising inhibitor (TRI) and a shrinkage reducing admixture (SRA) are adopted to improve the properties of HSHPC. The macroproperties of concrete are closely linked to its pore structure. In this paper, the effects of the water-to-cement ratio (w/c) and TRI and SRA contents on the pore size distribution (PSD) and porosity of early-age cement paste were tested by low-field nuclear magnetic resonance spectroscopy (LF-NMR). The test results showed that the PSDs of samples generally contain two peaks. The most probable pore diameter (MPPD) increases with the w/c and reduces with the TRI content and age. However, the MPPD changes only slightly with SRA content. For the same SRA or TRI content, the MPPD changes in samples containing both SRA and TRI are similar to those of samples with TRI or SRA only. However, the combined use of SRA and TRI has an apparent influence on the PSDs of samples. The porosity becomes large with the w/c and SRA content but declines with TRI content. The porosities of samples with both SRA and TRI addition are significantly lower than those of samples without the SRA and/or TRI at 28 days. A modified two-peaks model, which is adapted from the Shimomura and Maekawa model, is developed for cement pastes with the TRI and/or SRA. The curves of the modified two-peaks model coincide with the experimental data.

Energy Harvesting Using Thermocouple and Compressed Air.

In this paper, we describe the possibility of using the energy of a compressed air flow, where cryogenic temperatures are achieved within the flow behind the nozzle, when reaching a critical flow in order to maximize the energy gained. Compared to the energy of compressed air, the energy obtained thermoelectrically is negligible, but not zero. We are therefore primarily aiming to maximize the use of available energy sources. Behind the aperture separating regions with a pressure difference of several atmospheres, a supersonic flow with a large temperature drop develops. Based on the Seebeck effect, a thermocouple is placed in these low temperatures to create a thermoelectric voltage. This paper contains a mathematical-physical analysis for proper nozzle design, controlled gas expansion and ideal placement of a thermocouple within the flow for best utilization of the low temperature before a shockwave formation. If the gas flow passes through a perpendicular shockwave, the velocity drops sharply and the gas pressure rises, thereby increasing the temperature. In contrast, with a conical shockwave, such dramatic changes do not occur and the cooling effect is not impaired. This article also contains analyses for proper forming of the head shape of the thermocouple to avoid the formation of a detached shockwave, which causes temperature stagnation resulting in lower thermocouple cooling efficiency.

Numerical simulation of non-isothermal drainage flow of a viscous gas from a narrow channel

Drainage of a compressed viscous gas from a semi-sealed narrow conduit to a large container is a model problem of fundamental interest to fluid production from subsurface porous rocks. The low Mach number drainage flow exhibits behaviors contrary to predictions from conventional incompressible flow approximations. This work employs direct numerical simulation to study non-isothermal drainage flow from a semi-sealed narrow channel to a laterally bounded large container. The Navier–Stokes characteristic boundary conditions are implemented at the open boundary downstream in the computational domain to avoid spurious wave reflection. For a laterally bounded container, wave transport dominates the drainage process. It is shown that in the absence of an imposed temperature drop, thermal effect slows down the drainage process with adiabatic walls. With large enough temperature drop, thermal effect speeds up the drainage, and it also produces excess mass beyond that of the isothermal model. These thermal effects are consistent with the previous results for a laterally unbounded container in a linear theory.

Techno-economic analysis and multiobjective optimization of a novel proposal for addressing summer-supply challenges of district heating systems

A critical challenge of some district heating systems is too low summer demand, which results in a too low temperature at the consumption points. To prevent this large temperature drop along the path, the heat production plants have to oversupply hot water to the pipeline, which is itself problematic techno-economically. One more challenge of summer supply, if supplied by waste incineration plants, is that due to the low heating demand during the summer, there will be too much useless excess municipal solid waste at the disposal, causing further technical and economic issues. In the proposed concept of this study, an integrated district heating/cooling system is proposed to address both of these problems. For this, a solar-assisted chiller is utilized to not only take advantage of the excess waste of the power plant but also the excess hot water injected into the pipeline for cold supply. The research question is about the optimal sizing of the system. The sizing of the components of the system is carried out via a rigorous multiobjective genetic algorithm work package covering technical, economic, and environmental objectives, and then, the optimal design is techno-economic-environmentally analyzed. In summer, the velocity of hot water reaches the appropriate value of 0.8 m/s, and following the cold load supply, 67.8 kg/s extra mass flow rate of hot water with a temperature over 80 ℃ could feed the district heating system. Besides, at least 78 tonnes more waste will be burnt per day. It means challenges of the high amount of waste disposal, low velocity of hot water in district heating pipeline, and the high amount of waste heat will be solved, and the levelized cost of cooling production would decrease by 10%.

Non-contact experiments to quantify the microlayer evaporation heat transfer coefficient during isolated nucleate boiling regime

Experiments to understand the relationship between dynamics of superheat layer, microlayer evaporation and bubble growth process during single bubble formation under saturated pool boiling regime have been conducted. Thin film interferometer and rainbow schlieren deflectometry have been employed in tandem to simultaneously map the transient evolution of microlayer and superheat layer along with the bubble growth process. During initial time instances of growth process, heat flux dissipated in the microlayer region is determined to be as high as ~1 MW/m2 for the range of experimental conditions employed. As a result, a large temperature drop is observed in the microlayer region. As the bubble growth process enters its final stages, reduced temperature levels of the heated substrate result into a significant reduction in the depletion rate of the inner core region of microlayer, while the evaporation rate of its peripheral region is seen to increase. The consolidated evaporative heat transfer coefficient for the entire bubble cycle is determined to be ~140 kW/m2K for q″ = 50 kW/m2 and 170 kW/m2K for q″ = 80 kW/m2. The corresponding accommodation factor required for predicting the evaporative heat transfer coefficient values through kinetic theory-based model is determined to be ~0.015.

Measurement of High-temperature Thermophysical Properties of Bulk and Coatings Using Modulated Photothermal Radiometry

This paper presents the development of instrumentation for the measurement of high-temperature thermal conductivity of bulk and coatings using a modulated photothermal radiometry (MPR) method, where a sample is heated by an intensity-modulated laser to probe into different layers of the sample. While MPR has been previously established, most of the prior studies only focus on the measurement at room temperature. The MPR has not been well studied for measurements of bulk and coating materials at high temperatures, which are increasingly important for a multitude of applications, such as materials used in the concentrating solar power (CSP) plants and the nuclear reactors. MPR is a non-contact technique that utilizes the intrinsic thermal emission from the specimens for thermometry, which is favorable for measurements at high temperatures in harsh environment. The authors designed and utilized a sample holder suitable for high temperature measurement up to 973 K with good temperature uniformity within the sample. The high-temperature MPR setup was validated by measuring bulk materials with known thermal conductivity. The setup and technique were then extended to the measurement of black solar-absorbing coatings of 10 to 50 μm thick on various substrates by modulating the frequency of the laser heating beam and the thermal penetration depth. The studies showed that thermal conductivities of typical solar-absorbing coatings are 0.4 ~ 0.8 W m−1 K−1, indicating a possibly large temperature drop within the coating under high solar irradiation flux, such as over 1000-sun for central solar towers in CSP plants.

The friagem event in the central Amazon and its influence on micrometeorological variables and atmospheric chemistry

Abstract. In the period between 9 and 11 July 2014, a friagem event reached the Amazon region. On 11 July, the southwest flow related to the friagem converged with the easterly winds in the central Amazon. The interaction between these two distinct air masses formed a convection band, which intensified over the Manaus region and the Amazon Tall Tower Observatory (ATTO) site. The satellite images show the evolution of convective activity on 11 July, which led to 21 mm of precipitation at the ATTO site. Moreover, the arrival of the friagem caused a sudden drop in temperature and a predominance of southerly winds, which could be seen in Porto Velho between 7 and 8 July and in Manaus and the ATTO site from 9 to 11 July. The results of ERA-Interim reanalysis and Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) simulations show that this friagem event coming from the southwest, carries a mass of air with higher O3 and NO2 mixing ratios and lower CO mixing ratio compared to the air masses present in the central Amazon. At Lake Balbina, the friagem intensifies the local circulations, such as the breeze phenomena. In the Manaus region and at the ATTO site, the main effects of the friagem event are a decrease in the incoming solar radiation (due to intense cloud formation), a large temperature drop and a distinct change in surface O3 and CO2 mixing ratios. As the cold air of the friagem was just in the lower 500 m the most probable cause of this change is that a cold pool above the forest prevented vertical mixing causing accumulation of CO2 from respiration and very low O3 mixing ratio due to photochemistry reduction and limited mixing within the boundary layer.

Design and Operation Strategy of Micro Organic Rankine Cycle with Zeotropic Binary Mixtures for Low Grade Geothermal Energy

In this study, we proposed a micro ORC with zeotropic mixture of less than 20 kW using low-grade geothermal heat energy and investigated the power generation performance of 3 kinds of zeotropic working fluids with different vapor-liquid equilibrium. Simulations were carried out for 3 cases with a constant heat source temperature of 373K and flow rates of 3000, 7000 and 15000 kg/h. In the flow rate of the heat source was set to 7,000 kg/h, only 4 cases generated of power. For n-butane / ethanol = 0.7 / 0.3 was used as the working fluid, the power generation was 16.1 kW with 5.83% of the thermal efficiency which was higher than Carnot efficiency (4.28%). In the flow rate of 3,000 kg/h of heat source, by using n-butane / 1-propanol = 0.4 / 0.6 as the zeotropic working fluid, 6.52 kW could be generated. From the analysis using T-H and T-s diagrams, it is found that the zeotropic working fluid can effectively function as a temperature glide with composition change for low-grade geothermal heat sources with large temperature drop, and thus can be a power generation.

Impact of temperature variability on childhood allergic rhinitis in a subtropical city of China

BackgroundMany studies have shown an association of childhood respiratory diseases with short-term temperature variability such as diurnal temperature range (DTR) and temperature change between two neighboring days (TCN). However, the impact of temperature variability on allergic rhinitis (AR) has not been investigated so far. This study sought to evaluate the short-term effect of temperature variability (i.e., TCN and DTR) on AR, as well as to identify vulnerable subpopulations.MethodWe collected daily data on emergency room visits and outpatients for AR and weather variables in Hefei, China during 2014–2016. A distributed lag non-linear model that controlled for long-term trend and seasonality, mean temperature, relative humidity, day of week was used to fit the associations of AR with DTR and TCN. Stratified analyses by age, sex and occupation were also performed.ResultsDuring the study period, there were a total of 53,538 cases and the average values of DTR and TCN were 8.4 °C (range: 1.0 °C to 21.2 °C) and 0 °C (range: − 12.2 °C to 5.9 °C), respectively. While we did not observe an adverse effect of DTR on AR, TCN was significantly associated with increased risk of AR. Specifically, a large temperature drop between two adjacent days (3.8 °C, 5th percentile of TCN) has a delayed and short-lasting effect on AR, with the estimated relative risk of 1.02 (95% confidence interval: 1.01 to 1.04) at lag 12. Moreover, boys and children older than 15 years seemed to be more vulnerable to the effect of TCN.ConclusionsThis study provided evidence of an adverse effect of large temperature drops between two adjacent days on childhood AR. Attention paid to boys and older children may help prevent AR attacks.

Short-term effect of ambient temperature change on the risk of tuberculosis admissions: Assessments of two exposure metrics

BackgroundAlthough the effects of seasonal variations and ambient temperature on the incidence of tuberculosis (TB) have been well documented, it is still unknown whether ambient temperature change is an independent risk factor for TB. The aim of this study was to assess the association between ambient temperature change and the risk of TB admissions. MethodA distributed lag non-linear model (DLNM) combined with Poisson generalized linear regression model was performed to assess the association between ambient temperature change and the risk of TB admissions from 2014 to 2018 in Hefei, China. Two temperature change metrics including temperature change between neighboring days (TCN) and diurnal temperature range (DTR) were used to assess the effects of temperature change exposure. Subgroup analyses were performed by gender, age and season. Besides, the attributable risk was calculated to evaluated the public health significance. ResultsThe overall exposure-response curves suggested that there were statistically significant associations between two temperature change metrics and the risk of TB admissions. The maximum lag-specific relative risk (RR) of TB admissions was 1.088 (95%CI: 1.012–1.171, lag 4 day) for exposing to large temperature drop (TCN= −4 °C) in winter. Besides, the overall cumulative risk of TB admissions increased continuously and peaked at a lag of 7 days (RR=1.350, 95%CI: 1.120–1.628). Subgroup analysis suggested that exposure to large temperature drop had an adverse effect on TB admissions among males, females and adults. Similarly, large level of DTR exposure (DTR=15 °C) in spring also increased the risk of TB admissions on lag 0 day (RR=1.039, 95%CI: 1.016–1.063), and the cumulative RRs peaked at a lag of 1 days (RR=1.029, 95%CI: 1.012–1.047). We also found that females and elderly people were more vulnerable to the large level of DTR exposure. Additionally, the assessment of attributable risk suggested that taking target measures for the upcoming large temperature drop (b-AF = 4.17%, 95% eCI: 1.24%, 7.22%, b-AN = 1195) may achieve great public health benefits for TB prevention. ConclusionThis study suggests that ambient temperature change is associated with the risk of TB admissions. Besides, TCN may be a better predictor for the TB prevention and public health.

Effect of temperature on gas production from hydrate-bearing sediments by using a large 196-L reactor

Methane hydrate exploitation via depressurization for a reservoir with a bottom gas-rich zone was simulated using a large-sized three-dimensional hydrate simulator. A single vertical well system and a system with a combination of vertical and horizontal wells were employed to elucidate the different effects of horizontal and vertical wells on the exploitation process. The results showed that effect of promoting gas production using a horizontal well is not obvious for a high permeability reservoir. A large exploitation temperature drop may lead to ice blockage in the pipelines, and fracturing technology was introduced to solve this blockage problem. Experiments performed above and below the freezing point inferred that the decomposition of the hydrate in different areas of the reactor was not simultaneous, according to analysis of the temperature distribution of the entire reactor during the exploitation process. For exploitation above the freezing point, temperatures in the bottom of the reactor tend to maintain a low level and work against hydrate decomposition. However, for exploitation below the freezing point, the low-temperature area in the bottom of the reactor preferentially converts to ice. Heat release and salt precipitation promoted hydrate decomposition, and the decomposition rate was significantly accelerated.

(Invited) Electroluminescent Hyperbolic Cooling of Graphene Field Effect Transistors

Heat management is critical for the performance of most modern electronic devices. It was recently proposed that radiative heat transfer - which is usually negligible in the solid state - could be increased in hyperbolic metamaterials, i.e., materials having a hyperbolic electromagnetic dispersion relation. [1] However, artificial metamaterials can be difficult to fabricate and integrate.Fortunately, most of Van der Waals materials are natural hyperbolic metamaterials. Indeed, due to their anisotropic layered structure, the in-plane and out-of-plane optical phonon energy splitting results in a hyperbolic dispersion of light in the Resstrahlen bands. As a consequence, in these materials, the strong light-matter coupling can give rise to a 102-105 increase in the e.m. local density of states, resulting in a dramatic enhancement of the radiative heat transfer. Moreover, the radiative character of heat exchange results in a propagative heat transport via hyperbolic phonon-polariton (HPhP) modes on micrometric scales.We have studied heat transfer in graphene on hexagonal boron nitride: a natural 2D hyperbolic material. In our devices, graphene is used as a versatile heat source in the near field of a hyperbolic material, and as a sensitive noise thermometer. [2] Using mono-, bi- and trilayer graphene, we demonstrate a strong increase of the electron gas cooling resulting in a large temperature drop when the emission of HPhP sets in. This process shares many analogies with electroluminescence, except that it involves near-field modes. We experimentally evidence that the case of graphene is unique, with cooling powers reaching few milliwatts per micron square [3], i.e., nine orders of magnitude larger than previously reported in the literature. Bibliography [1] S. Biehs, et al "Hyperbolic metamaterials as an analog of a blackbody in the near field." Phys. Rev. Lett. 109, 104301 (2012)[2] W. Yang, et al "A Graphene Zener–Klein Transistor Cooled by a Hyperbolic Substrate." Nat. Nanotech. 13, 47 (2018)[3] E. Baudin, et al "Hyperbolic Phonon Polariton Electroluminescence as an Electronic Cooling Pathway", Adv. Funct. Mat.1904783 (2019) Figure 1

Study on the Effect of the Obstacle on Heat Transfer Oxidation Spontaneous Combustion Characteristic of Coal Gangue Fracture

ABSTRACT To address the coal gangue fracture heat transfer problem, the law of heat transfers and temperature distribution in the coal gangue fracture is studied. The temperature distribution in a coal gangue fracture under 12 conditions (with or without the obstacle, and various heat flows) is simulated via Fluent numerical simulation. The results show that the heat flow velocity, temperature and obstacle are important factors in inhibiting heat transfer oxidation spontaneous combustion in the coal gangue fracture. When the heat flow temperature is constant, the low-velocity heat flow causes a large temperature drops in the coal gangue fracture; when the heat flow velocity is constant, the high-temperature heat flow also produces a large temperature drops effect; when the obstacle is present and the heat flow produces vortex pass through the obstacle, increasing the energy loss in the coal gangue fracture, causing the temperature in the coal gangue fracture to drop rapidly, and reach the lowest in the position of the obstacle. Obstacles can effectively inhibit the heat transfer characteristics in the coal gangue fracture and reduce the risks of oxidation spontaneous combustion of gangue after grouting.

Thermodynamics of the insulator-metal transition in dense liquid deuterium

Recent dynamic compression experiments [M. D. Knudson et al., Science 348, 1455 (2015); P. M. Celliers et al., Science 361, 677 (2018)] have observed the insulator-metal transition in dense liquid deuterium, but with an approximately 95-GPa difference in the quoted pressures for the transition at comparable estimated temperatures. It was claimed in the latter of these two papers that a very large latent heat effect on the temperature was overlooked in the first, requiring correction of those temperatures downward by a factor of 2, thereby putting both experiments on the same theoretical phase boundary and reconciling the pressure discrepancy. We have performed extensive path-integral molecular dynamics calculations with density functional theory to directly calculate the isentropic temperature drop due to latent heat in the insulator-metal transition for dense liquid deuterium and show that this large temperature drop is not consistent with the underlying thermodynamics.