Historically, combustion modeling is important for many transportation- and ground-based applications. More recently, modeling has been offered as an early screening tool in the evaluation of a potential alternative aviation jet fuel. This combustion evaluation path would in theory be conducted by gas turbine Original Equipment Manufacturers (OEMs) on proprietary geometries and conditions. Ideally, OEMs would have access to the latest combustion theory models and would thus have the highest predictive confidence in their model predictions. Unfortunately, the latest combustion theory codes are not written for commercial purposes. This work identifies and develops a conduit for OEM usage of latest flamelet theory for use in the evaluation of alternative jet fuel combustion properties. A so-called “common format routine” (CFR) software with two low-dimensional manifold combustion models that can be used for laminar and turbulent applications is developed, which can be implemented by OEMs on proprietary hardware. The two models are the flamelet prolongation of the intrinsic low-dimensional manifold (FPI), used for premixed combustion, and the flamelet progress variable (FPV), utilized for nonpremixed combustion. The three branches of combustion are computed using a hybrid tool that combines homotopic flamelet calculations with scaling laws and the two- and one-point flamelet continuation methods in order to resolve bifurcations. The mixture fraction and progress variable definitions can be chosen to be any summation of atomic and species composition, respectively. Diffusivity coefficients can be computed using unity Lewis number, mixture-averaged and multicomponent species composition. The turbulence-chemistry interaction is tabulated a priori using Beta probability density function (PDF) for the mixture fraction and Beta or Dirac-delta PDF for the progress variable. Parallel computing is necessary for industrial quality tabulation. The tabulated table can be used for k-ε and k-ω RANS, SAS, DES, and LES simulations. The software can also interact with liquid spray and exchange mass between the liquid and gaseous phase. The software is verified against previous numerical simulations of canonical triple flames, piloted flames and single-cup combustor. The numerical results are validated against experimental measurements of temperature and species mass fractions. The CFR software advances Cantera 2.3. Hence, the software contains an inner layer of C++ code, an intermediate layer of Python wrappers, and an upper layer (GUI) of C# code. The pre-tabulated chemistry is used for CFD simulations. The tables are bi-linearly interpolated for laminar simulations and tri-linearly interpolated for turbulent simulations. The tabulated chemistry can be hooked to commercial software such as Fluent through C and Scheme codes. The simulated flames presented here were computed with this software. The developed software is reliable for modeling and simulation of complex combustion phenomena.

Reduced mechanisms are needed for use with computational fluid dynamic codes (CFD) utilized in the design of combustors. Typically, the reduced mechanisms are created from the detailed mechanisms which contain numerous species and reactions that are computationally difficult to handle using most CFD codes. Recently, it has been shown that the detailed Aramco 2.0 mechanism well predicted the available experimental data at high pressures and in high-CO 2 diluted methane mixtures. Further, a 23-species gas-phase mechanism is derived from the detailed Aramco 2.0 mechanism by path-flux-analysis method (PFA) by using CHEM-RC. It is identified that the reaction CH 4 +HO 2 ⇔ CH 3 +H 2 O 2 is very crucial in predicting the ignition delay times under current conditions. Further, it is inferred that species C 2 H 3 and CH 3 OH are very important in predicting the ignition delay time of lean sCO 2 methane mixtures. Also, the 23-species mechanism presented in this work is performing on par with the detailed Aramco 2.0 mechanism in-terms of simulating ignition delay times, perfectly-stirred-reactor estimates under various CO 2 dilutions and equivalence ratios, and prediction of turbulence chemistry interactions. It is observed that the choice of equation-of-state has no significant impact on the ignition delay times of supercritical CH 4 /O 2 /CO 2 mixtures but it influences supercritical H 2 /O 2 /CO 2 mixtures considered in this work.

In order to reduce CO 2 emission from thermal power stations with keeping high thermal efficiency, a new concept of IGCC system, namely oxy-fuel IGCC, has been recently proposed. Hence CO 2 is recycled in the system, the effect of CO 2 recycle on each equipments should be clarified. In this study, the effect of recycled CO 2 injection on coal gasifier performance was investigated by means of three-dimensional RANS-based numerical simulation. For estimating of coal gasifier performance, coal gasification and water-gas shift reaction are key phenomena. Therefore, the partially active site sharing coal gasification model and detailed chemistry of water-gas shift reaction model were implemented. Calculated gasifier was a commercial scale entrained flow coal gasifier whose coal feeding rate is 70 tons per hour. The gasifier consists of a lower combustor part and an upper reductor part. The effect of coal feeding rate into the reductor, R/T, was investigated. The results show that temperature in the combustor decreases with decreasing R/T. In the lower R/T condition, hence air ratio in the combustor decreases, the reducing atmosphere becomes stronger. As a result, coal gasification which is endothermic reaction in the combustor is promoted. Although coal gasification is occurred in the reductor in higher R/T condition, total coal gasification rate is not so promoted compared with lower R/T condition. Due to the above mechanism, the gasification performance becomes higher with decreasing R/T. The results obtained in this study indicate that it is important that how much the higher gasification reactivity in a gasifier is exploited by optimizing local heat balance.

We reported the large-eddy simulations of a series of bluff-body flames varying air-fuel velocity ratio. The air-fuel ratio γ is defined by the ratio of external air velocity to central jet velocity, ranging from 0.05 to 0.50. The case of γ = 0.32 is exactly same the Sydney bluff-body HM1e flame. Firstly, the mathematical model and numerical method were validated in details as the simulation results are all in good agreement with measurements in HM1e flame. Then the interaction between turbulence and thermo-chemistry is revealed. As γ increases, external coflow trends to dominant the flame behavior. The stoichiometric mixture fraction shifts from the area between recirculation zone and central jet to the area between external flow and recirculation zone. Corresponding, the flame changes from jet-like, columnar to hat-like flames. The different level of local extinction and reignition is also observed. Local extinction and reignition occurs in jet-like and columnar flames. As γ increases, local extinction becomes easier and reignition becomes harder.

This paper proposed an approach to modeling alkali metal reacting dynamics in turbulent pulverized-coal combustion (PCC) using tabulated sodium chemistry. With tabulation, detailed sodium chemistry can be incorporated in large-eddy simulation (LES), but the expenses of solving stiff Arrhenius equations can be avoided. The sodium release rate from a pulverized-coal particle is assumed to be proportional to the pyrolysis rate, as a simplification. The chemical forms of released sodium is assumed to be atomic sodium Na, because atomic sodium is predicted to be the favoured species in a flame environment. A detailed sodium chemistry mechanism including 5 sodium species, i.e., Na, NaO, NaO 2 , NaOH and Na 2 O 2 H 2 , and 24 elementary reactions is tabulated. The sodium chemistry table contains four coordinates, i.e., the equivalence ratio, the mass fraction of the sodium element, the gas-phase temperature, and the progress variable. Apart from the reactions of sodium species, hydrocarbon volatile combustion has been modeled by a partially stirred reactor concept. Since the magnitude of sodium species is very small, i.e., at the ppm level, and the reactions of sodium species are slower than volatile combustion, one-way coupling is used for the interaction between the sodium reactions and volatile combustion, i.e., the former having no influence on the latter. A verification study has been performed to compare the predictions on sodium species evolutions in zero-dimensional simulations using the chemistry table against directly using the detailed sodium mechanism under various initial conditions, and their agreement is always good. The PCC-LES solver used in the present study is validated on a pulverized-coal jet flame ignited by a preheated gas flow. Good agreements between the experimental measurements and the LES results have been achieved on gas temperature, coal burnout and lift-off height. Finally, the sodium chemistry table is incorporated into the LES solver to model sodium reacting dynamics in turbulent pulverized-coal combustion. Properties of Loy Yang brown coal, for which sodium data are available, are used. Characteristics of the reacting dynamics of the 5 sodium species in a pulverized-coal jet flame are then obtained. The results show that Na and NaOH are the two major sodium species in the pulverized-coal jet flame. Na, the atomic sodium, has a high concentration in fuel-rich regions; while the highest NaOH concentration is found in regions close to the stoichiometric condition. It should be pointed out that the proposed chemistry tabulation approach can be extended to modeling potassium reacting dynamics in turbulent multiphase biomass combustion. (CSPE)

For achieving efficient oxy-coal combustion in a MILD (Moderate or Intense Low Oxygen Dilution) state, the optimum operating conditions with high-velocity jets in a lab-scale cylindrical furnace (Φ200mm×2000mm) was determined. The mesoscopic characteristics of turbulent and flame behavior under different jet design and jet spacing were simulated and compared. The results show that L=30∼60mm(O 2 side) and L=60mm(O 2 center) conditions are recommended as oxy-coal MILD combustion as well as IFRF furnace condition, the flame front locates in distributed regime, the global regime was depict as 1 < l/l F < 4, 60 < Re T < 150 and 50 < Ka < 500 ; for flaming conditions, the flame front locates in small-scale turbulent regime or thin reaction zone, the global regime was depicted as 0.5 < l/l F < 4, 40 < Re T < 110 and 30 < Ka < 900 ; with high-velocity oxygen jet technology, the combustion process is in slow chemistry regime (Da << 1), governed by chemical-kinetic mechanism; large spacing (L=75mm) is not favored for co-flow burners due to poor radial mixing as well as the restriction of wall.

Water cooled steam turbine-generator stator systems are subject to flow restrictions and pluggage by copper that originates from within the stators. Deposition may occur within hollow stator bars or coils, or in filters or screens in the water flow circuit. In extreme cases of deposition, flow restriction can cause the generator to overheat due to reduction of cooling flow, resulting in unit outages and potentially serious equipment damage. Chemistry programs to minimize corrosion and transport of copper within the system include high oxygen, low oxygen, and alkaline (pH elevation). In all cases high purity water is required for the application. Examination of copper deposits can provide clues to the adequacy of the chemistry treatment program for minimizing system corrosion.

The results obtained from the modeling of thermal partial oxidation of kerosene based Jet-A fuel are presented using one dimensional chemical modeling. Two detailed kinetic models for alkenes chemistry ranging between C8 to C16 were evaluated and compared against experimental data of thermal partial oxidation of Jet-A fuel. The key difference between these two kinetic models was the inclusion of model for soot formation reactions. Chemical modeling was performed using dodecane to represent Jet-A fuel. The results showed that the model with soot reactions was significantly more accurate in predicting reformate products from Jet-A. In particular, the formation of carbon monoxide, methane and acetylene closely followed the experimental data with the model that included soot formation reactions. The results revealed that the soot formation reactions promoted the smaller hydrocarbons to decompose via the alternate kinetic pathways and from additional radical formation. The results also reveal that the inclusions of soot formation reactions are critical in the modeling of thermal partial oxidation of fuels for fuel reforming.

New power generation in the U.S. is being dominated by installation of combined-cycle power plants, where a significant portion of the power is produced from steam turbines supplied by heat recovery steam generators (HRSG). Proper chemistry control and monitoring of HRSG feedwater, boiler water, and steam are essential for high reliability and availability of these units. However, many plants have minimal staff, most if not all of whom have no formal chemistry training and who may not fully understand the importance of water/steam chemistry and monitoring techniques. This paper provides an outline of the most important chemistry control methods and also examines the phenomenon of flow-accelerated corrosion (FAC). FAC is the leading cause of corrosion in HRSGs,[1] and is often the result of the outdated belief that oxygen scavengers are a requirement for feedwater treatment. Since 1986, FAC-induced failures at several coal-fired power plants have killed or injured a number of U.S. utility workers.

Two types of flow-driven wear phenomena are a frequent source of failures in Heat Recovery Steam Generators (HRSGs): Flow-Accelerated Corrosion (FAC) and Liquid-Droplet Impingement (LDI). The two mechanisms combined are also known by an older term, erosion-corrosion. This better describes what can be viewed as a continuum of mechanisms, driven by chemistry and/or fluid velocity, which lead to wear and consequent thinning of pipe walls. One common failure location in the HRSG is in Low Pressure (LP) Evaporator circuits, both in regions with two-phase and with single-phase flow conditions. Replacement and/or redesign of the LP Evaporator system is often required. Water chemistry is known to be a key factor in determining the risk of FAC; it can be modified if required during operation to potentially affect wear rates. Another key factor, determined at the design stage, is the chrome content of the steel. The emphasis here is on evaluating other design factors, particularly local process conditions throughout the LP Evaporator circuit, that affect susceptibility to FAC and LDI. LP systems today often are designed to operate at very low pressures (< 3 barg, 45 psi) with the goal of extracting the last practical amount of thermal energy from gas turbine exhaust gas. Furthermore, many combined cycle power plants (such as those in combined power and desalinization service) have variable loads that lead to wide variations in LP operating pressures. The overall bulk fluid circulation in natural circulation LP Evaporators of several different HRSG designs is evaluated over a range of operating conditions. These circulation calculations are sensitive to small changes in heat transfer and load conditions at low pressures, due to the high void fraction in the two-phase region. An accurate estimation of void fraction is therefore required to determine local process conditions (flow velocities and flow regimes) in this region. The limitations of some of the common methods for estimating void fractions, such as asymptotic values for high void fractions at low pressures, are considered. The evaporator process conditions determined by modeling are used as inputs to assess the potential for wear by FAC and/or LDI using several established methods (Kastner, Sanchez-Caldera). The results are compared with case studies from field investigations to assess if wall thinning encountered in actual HRSG service can be correlated with certain design factors.

The aim of this investigation is to determine the effects of confinement on the stabilization of turbulent, lifted methane (CH 4 ) jet flames. A confinement cylinder (stainless steel) separates the coflow from the ambient air and restricts excess room air from being entrained into the combustion chamber, and thus produces varying stabilization patterns. The experiments were executed using fully confined, semi-confined, and unconfined conditions, as well as by varying fuel flow rate and coflow velocity (ambient air flowing in the same direction as the fuel jet). Methane flames experience liftoff and blowout at well-known conditions for unconfined jets, however, it was determined that with semi-confined conditions the flame does not experience blowout. Instead of the conventional unconfined stabilization patterns, an intense, intermittent behavior of the flame was observed. This sporadic behavior of the flame, while under semi-confinement, was determined to be a result from the restricted oxidizer access as well as the asymmetrical boundary layer that forms due to the viewing window. While under full confinement the flame behaved in a similar method as while under no confinement (full ambient air access). The stable nature of the flame while fully confined lacked the expected change in leading edge fluctuations that normally occur in turbulent jet flames. These behaviors address the combustion chemistry (lack of oxygen), turbulent mixing, and heat release that combine to produce the observed phenomena.

The PHEBUS-FP program is an outstanding example of an international cooperative research program that is yielding valuable data for validating severe accident analysis computer codes. The main objective of the PHEBUS FPT1 experiment was to study the processes in the overheated reactor core, release of fission products and their subsequent transport and deposition under conditions representative of a severe accident of a Pressurised Water Reactor. The FPT1 test could be divided in the bundle degradation, aerosol, washing and chemistry phases. The objective of this article is the best estimate analysis of the bundle degradation phase. GRS (Germany) best estimate method with the statistic tool SUSA used for uncertainty and sensitivity analysis of calculation results and RELAP/SCDAPSIM code, designed to predict the behaviour of reactor systems during severe accident conditions, was used for the simulation of this test. The RELAP/SCDAPSIM calculation results were compared with the experimental measurements and calculations results, received by employing ICARE module of ASTEC V2 code. The performed analysis demonstrated, that the best estimate method, employing RELAP/SCDAPSIM and SUSA codes, is capable to model main severe accidents phenomena in the fuel bundle during the overheating and melting of reactor core.

Scientific bases for corrosion control for water-cooled fusion reactors, such as ITER, are discussed in this paper. In the previous overview papers [1,2], the author has identified that ‘long cell action’ corrosion plays a pivotal role in practically all unresolved corrosion issues, irrespective of fission reactor types and operation. In trying to confirm the existence of radiation-induced ‘long-cell’ action (macro) corrosion cell in the primary cooling system of LWRs, the author attempted to theoretically reproduce the electrochemical potential differences demonstrated during experiments at the INCA Loop in Sweden and the NRI-Rez Loop in the Czech Republic [3,4]. Based on these knowledge bases, characterization of water chemistry for fusion was made through radiation- and electro-chemistry analysis following the methodology explained in the companion paper also presented at this conference [5]. Approximately 70 mV of potential difference is predicted between the high dose rate and the out-of-flux regions through the illustrative model examined in this paper, which supports the existence of the LGCA mechanism. This value is about 1/5 of the potential difference for a typical PWR. For further verification of this approach, ‘international benchmark in-pile tests’ are highly awaited. Further optimization studies as well as material testing under the influence of the LGCA mechanism should be performed to establish corrosion control.

Nickel and nickel base alloys have been widely used as structural materials in nuclear power systems, because they have favorable material properties at high temperature water environment. Recently, however, these materials have shown to be suffered from primary water stress corrosion cracking (PWSCC) in pressurized water reactor environments. But there is no general theory to explain the mechanism of PWSCC in nickel base alloys, because the process of PWSCC usually takes place slowly in tiny localized area and many difficulties to maintain specific environment of nuclear power plants chemistry are involved. In this study, ab-initio calculations on the diffusion processes of oxygen in nickel and Ni-Cr binary alloy are conducted to understand the oxidation behavior of nickel base alloys. Total energies, forces, and energy profiles are calculated using the density functional theory (DFT) in this study. Then, the cohesive energy, insertion energy of atomic oxygen and vacancy formation energy in nickel are calculated and compared with experimental data. The activation energy of oxygen which is important parameter to understand the diffusion behavior, are also calculated. The results are good agreement with previous work for the diffusion of oxygen in pure nickel. However, the calculated activation energy for diffusion of oxygen in Ni-Cr binary alloy showed lower value than that in nickel because of current limitation of calculational model in this study. The current model will be improved by further investigation considering oxide formation.

In a series of recently published papers [1,2], the author tried to elucidate on the corrosion environment of LWR cores. Through these studies, the reactor cores are found to be behaving as gigantic cathodes. He established that “long cell action” (a kin to “macro-cell”) corrosion plays a pivotal role in practically all unresolved corrosion issues, irrespective of reactor types and operation [3,4]. The author recently developed a unified theory, which enables the estimating of redox potentials for all types of LWRs (e.g., PWR, BWR, VVER, and RBMK). The author’s previous calculations are confirmed by applying a new set of g -values and reaction kinetics data set [i.e., AECL 153-127160-450-001], developed by Drs. A.J. Elliot and S.M. Bartels in 2009. The results show reasonable agreement with the published in-pile experimental results. However, the author’s calculated DO as well as DH resulted in significant deviations from the input data. The author tried to fortify the verification through another approach in this paper, by incorporating electrolysis reactions (i.e., Faraday’s law) induced by the potential difference. By integrating the radiation-chemical rate equations with the electrolysis reactions, the electric current flowing between the in-core and the out-flux regions through structures was estimated. It was found that this configuration induces surprisingly strong “long cell” current (i.e., cathode current) outside of the regions of DH and DO commonly specified by the water chemistry conditions. This current determines many of the basic corrosion parameters, including ECP, redox potentials, pH, DO and DH, as well as over-potentials, through water chemistry specifications. Although details are still debatable, the author believes that there is no doubt that this corrosion mechanism exists in water-cooled reactors. However it remains debatable due to the lack of basic knowledge pertaining to the chemistry of the LWR cores.

From a crud deposition perspective the achievement of zero fuel failures requires the integration of core neutronics, core thermal-hydraulics, and plant chemistry disciplines. The various level of detail required in the assessment of crud risk is based on guidelines and a checklist developed and published by EPRI. In the guidelines EPRI defined two levels of assessment where core neutronics and thermal-hydraulics are coupled with plant chemistry. These two levels are called Levels III and IV in the EPRI guidelines. AREVA developed a process using the standard licensing tools and a number of specialized application tools and interfaces that allow Level III and IV calculations. The Level III calculations are performed using a typical reload licensing subchannel node scale (scale of several centimeters) whereas the Level IV calculations are performed on fractions of a millimeter scale. This paper provides an overview of the neutronics and thermal-hydraulic process used to perform Levels III and IV assessments and provides some results for a typical B&W-designed 177-fuel assembly operating plant. This same process could be applied to other plant types. The details of the plant chemistry process are not covered in this paper, as they are covered in other publications.

This paper summarizes the analysis of loss of coolant accident (LOCA) frequencies in support of a risk-informed (RI) evaluation of Generic Safety Issue (GSI) 191 for the South Texas Project Electric Generating Station (STPEGS) Units 1 and 2. The STP RI-GSI 191 Closure Study investigates the size and location of loss of coolant accidents (LOCAs) more finely than in traditional PRAs in order to assess the risk of debris formation during the LOCAs that could interfere with the operation of the emergency core cooling systems (ECCSs) or inhibit coolant flow through the core during the recirculation phase after a LOCA. The size and location of the break could influence the amount and chemistry of debris formation and the timing and need for actions to initiate or terminate containment sprays and recirculation cooling. This application requires the capability to estimate LOCA frequencies as a function of break size at each location within the Class 1 pressure boundary with due regard to the proper characterization and quantification of uncertainties.

The combustion of CO 2 neutral solid fuels like biomass and waste-based fuels with circulating fluidized bed (CFB) boiler designs has become an accepted way to generate electric power and process steam to reduce global CO 2 emissions (i.e. reduce “carbon footprint”) and hence to reduce the potential impact on climate change. In the European Union, for example, there is a co-combustion directive to encourage the use of biomass and waste as energy sources with the co-firing of coal. Quite often biomass and waste combustion in CFB’s have unique technical challenges when compared to fossil fuels. The technical challenges of firing these CO 2 neutral fuels do impact CFB boiler design and may impact plant lifecycle and reliability when compared to coal. Among these are combustion bed agglomeration, furnace and heating surface slagging, and new forms of corrosion potential. However, when co-firing these CO 2 neutral fuels with coal, these challenges can be tempered in a positive way through inherent changes in the flue gas chemistry and other design considerations. Co-firing makes sense. In addition to reducing the carbon footprint of a boiler project through use of biomass and waste, these energy sources can have a significant positive impact on plant financials owing to low cost supply. However these fuels can have wide variations in availability and energy content over the course of the many years of a boiler’s life. As such, maintaining coal as a supplemental fuel or back-up fuel also provides significant benefit in terms of guaranteeing the energy input supply and thereby securing plant availability. This benefit can help lower project financial risk and improve financial attractiveness and viability. This paper describes this type of boiler, its design considerations and operating history. Highlighted herein is the operating facility in Pori, Finland, commissioned in 2008, which is a 60 MWe CFB boiler burning peat, biomass and recycled waste fuel (RDF) with coal as a back-up fuel. Other facilities with similar design and with operating history of over 10 years are included as reference.

In swirl stabilized burner, combustion induced vortex breakdown (CIVB) flashback is a significant phenomenon. This paper presents experimental measurements of CIVB flashback propensity for hydrogen (H 2 )-carbon monoxide (CO) flames. The effects of H 2 concentration, and swirl number on the flashback propensity of H 2 -CO flames are discussed. For a given air mass flow rate, the stoichiometric ratio (%F) at which the CIVB flashback occurs decreases with the increase in H 2 concentration in fuel mixtures. However it appears that near the CIVB flashback limit, the swirl strength plays a more dominating role over the H 2 concentration in the fuel mixture. The flashback propensity decreases with the increase in swirl number. An analysis of the nonreacting flow field (Air 6 g/s) as well as reacting (CH 4 -Air and H 2 -CO-Air) flame near the CIVB transient velocity field was conducted. The analysis revealed that a complex vortex-chemistry interaction leading to vortex breakdown and flashback occurred. The vector flow field showed that the high swirling flow generates a more stabilized and wider recirculation zone. It also showed that the presence of H 2 dictates the intensity of the flashback process.

A station uprate provides an economical opportunity to improve the generation capacity of a power plant if all the major system components are able to handle the effects of increased generation. The magnitude of uprate from increased steam generation will be limited by the maximum capacity of the weakest link in the cycle, which for many plants is the condenser. The condensers on many units are already pushed to their limit. This is especially true if a cooling tower is employed, where the condenser inlet cooling water temperatures are high on high wet-bulb temperature days. This condition forces many units to throttle down load to prevent excursions above the backpressure limits on their turbines. For condensers limited by the present duty, however, the options have been historically limited to rebundling the whole condenser with a larger surface area design and perhaps changing the tube material to a material with a higher heat transfer coefficient. Recently, a very low cost option has been demonstrated that should be considered by any plant looking to increase condenser duty or prevent station power reductions. Advances in the proper management of steam, condensate and noncondensable flows have permitted an upgrade for almost all vintage condensers, unlocking inactive surface area without a bundle replacement or complete redesign. This paper reports the results of a condenser retrofit effort, with emphasis on an upgrade applied to a load limited condenser concurrent with a major reduction in its operating backpressure. The performance of the condenser is presented before and after the upgrade showing significant backpressure reduction and heat transfer improvement accompanied by exceptional condensate chemistry results. It will be shown that 30% of the effective condenser surface area (or similarly, an additional 30% average heat transfer coefficient) was unlocked by activating the previously idle surface area.