Cool-down Process Research Articles

Relative-Air Humidity Sensing Element Based on Heat Transfer of a Single Micromachined Floating Polysilicon Resistor

An air-humidity sensing element based on heat transfer mechanisms (conduction and convection) is presented. The sensing element is a single floating resistor of doped polysilicon, which operates in two phases: thermal actuation and thermal sensing. As thermal actuation, a convenient biasing current is applied to the resistor leading its self-heating by Joule Effect. As thermal sensing, the resistor biasing current is reduced and its Thermal Time Constant (τ) during the cool-down process is measured. Characterization results show that τ is closely related to the air relative humidity (%RH). This sensor presents a maximum power consumption of 5 mW.

Boil-off gas balanced method of cool down for liquefied natural gas tanks at sea

Cooling down the cargo tanks of liquefied natural gas carriers (LNGC) prior to the ships arrival at discharge and loading ports follow various widely adopted operating procedures. The tank cool-down procedures typically followed cannot though be considered as best practice, because they consume considerable boil-off gas while reducing tank temperatures. An alternative tested method, described here, consumes considerably less liquefied natural gas (LNG) during the tank cool-down process, which is beneficial, particularly during the ballast voyages. In certain circumstances, LNGC consume liquid marine fuels so that they are able to preserve enough LNG heel to complete tank cool down at sea to required low temperatures before reloading can be commenced. The novel method devised for cooling down LNGC, particularly those fitted with membrane cargo tanks, at sea prior to arrival at a loading terminal involves much lower LNG heel consumption than conventional methods. The boil-off gas (BOG)-balanced tank-cool-down method applies continuous spraying, at very low rates, of the tanks with LNG extracted from the heel. This procedure enables the ship’s engines to consume all excess BOG without the need to pass some of it as waste for combustion in the gas combustion unit or steam dump. It also ensures that the LNG cargo tanks are maintained at stable and constant pressure and reduces the coolant LNG quantity consumed. The BOG-balanced tank-cool-down is straightforward to implement and monitor, simplifying tank pressure control. Test results demonstrate that tank cool-down rates of 4 to 5 ◦C/per hour can be maintained such that tank temperatures can be reduced from +30 to -130 ◦C within 37 hours. The method could work on LNGC with Moss-type tanks but is likely to be less effective as they are typically fitted with fewer tank spraying nozzles. Cited as : Kulitsa, M., Wood, D.A. Boil-off gas balanced method of cool down for liquefied natural gas tanks at sea. Advances in Geo-Energy Research, 2020, 4(2): 199-206, doi: 10.26804/ager.2020.02.08

An efficient semi-analytical framework to tailor snap-through loads in bistable variable stiffness laminates

Multistable laminates are potential candidates for adaptive structures due to the existence of multiple stable states. Commonly, such bistable shapes are generated from the cool-down process of the unsymmetric laminates from the curing temperature. In this work, we exploit unsymmetric variable stiffness laminates with curvilinear fiber paths to generate similar bistable shapes as unsymmetric cross-ply laminates, but with the possibility to tailor the snap-through loads. Snap-through is a complex phenomenon in that is difficult to characterize using simple analytical models. An accurate yet computationally efficient semi-analytical model is proposed to compute the snap-through forces of bistable variable stiffness (VS) laminates. The differential equations resulting from the compatibility and the in-plane equilibrium equations are solved with negligible numerical error using the Differential Quadrature Method (DQM). As a result, the in-plane stress resultants and the total potential energy is written in terms of curvatures. The out-of-plane displacements are expressed in the form of Legendre polynomials where the unknown coefficients of the displacement function are found using the Rayleigh-Ritz formulation. The calculated snap-through loads are then compared with the Finite Element (FE) results. A parametric study is conducted to explore the tailoring capabilities of VS laminates for snap-through loads.

Investigation of improving cool-down speed of Stirling type pulse tube cryocooler with ambient displacers

For a cryocooler, besides high efficiency at the working temperature, the cool-down speed is also important for some applications. Because of the difference in structure and operating mechanism, different cryocoolers have different characteristics for cool-down speed. This work introduces a Stirling type pulse tube cryocooler with ambient displacers which works in the liquid nitrogen temperature region. Strategies for improving the cool-down speed from room temperature to liquid nitrogen temperature have been investigated through simulation. The pulse tube cryocooler is designed to provide a nominal cooling power of 17.8 W at 77 K with 232.5 W of input electric power at 70 Hz. By fixing the maximum displacer movement in the simulation, the characteristics of how tuning the frequency around 70 Hz can change the cool-down speed without exceeding the allowable displacement of the piston and the current draw of the actual compressor are investigated. The strategy for tuning both the frequency and voltage turns out be effective in the beginning stage of the cool-down process with an improvement of the cooling power by about 15%-20%. The gain becomes less obvious as the cold head temperature drops. In conclusion, tuning both the frequency and voltage during the cool-down process helps the cold-head to reach its final temperature faster but the average gain is not as big as expected.

Structural Assessment of the DTT Poloidal Field Coil System

In the context of the European fusion roadmap, the divertor tokamak test (DTT) experimental reactor is intended to investigate alternative divertor configurations in view of the EU-DEMO power exhaust handling necessities. The six poloidal field coils of this tokamak are responsible for the plasma shape and equilibrium, and numerous steps were taken to obtain a design that is magnetically consistent with plasma requirements and structurally compliant with the chosen failure criterion. This work presents the structural assessment that has been performed on the poloidal coil system, taking into account the cooldown process, the energisation to operating conditions and fatigue. Finite Element Analysis has been employed as the principal means of investigation.

Energy saving potential with smart thermostats in low-energy homes in cold climate

Smart home systems with smart thermostats have been used for years. Although initially mostly installed for improving comfort, their energy saving potential has become a renowned topic. The main potential lies in temperature reduction during the times people are not home, which can be detected by positioning their phones. Even if the locating is precise, the maximum time people are away from home is short in comparison to the buildings’ time constants. The gaps are shortened by the smart thermostats, which start to heat up hours before occupancy to ensure comfort temperatures at arrival, and low losses through high insulation and heat-recovery ventilation in new buildings, which slow down the cool-down process additional to the thermal mass. Therefore, it is not clear how high the actual savings can be for smart thermostats in new buildings. In this work, a smart radiator valve was installed for a radiator in a test building. Temperature setback measurements were used to calibrate a simulation model in IDA ICE. A simulation analysis was carried out for estimating the energy saving potential in a cold climate for different usage profiles.

A two-stage Stirling cryocooler capable of providing more than 100 W cooling power at 30 K

Regenerative cryocoolers with large cooling capacity at 30 K have a promising prospect in the fields of superconducting technology and gas liquefaction. Compared with other types of cryocoolers, Stirling cryocoolers have the advantages of high cooling capacity, high efficiency, fast cool-down process and compact configuration. A two-stage Stirling cryocooler with large cooling capacity driven by the crank-rod mechanism is developed based on the Sage simulation results, and the preliminary experimental results are presented. Firstly, the pressure characteristics under different working conditions are investigated. The amplitude of the pressure and the pressure ratio at the compression chamber increases as the charging pressure increases. Increasing the refrigeration temperature of the second stage results in the decrease of the pressure amplitude, and the decreasing rate increases as the heat load on the first stage increases. Then, the performance of the ambient heat exchanger is studied. As the charging pressure increases from 2.2 to 2.6 MPa, the heat rejected from the ambient heat exchanger increases from 7.57 to 9.19 kW when there are no heat loads at the two stages of the cryocooler. The heat rejected from the ambient heat exchanger increases by 400 W with every increase of 0.1 MPa of charging pressure. With the increase of the refrigeration temperature of the second stage, the heat rejected from the ambient heat exchanger decreases, and the decreasing rate increases as the heat load on the first stage increases. Furthermore, the influence of the variation of the charging pressure and heat loads at the two stages on the cooling performance is introduced. The temperature of the second-stage cold end heat exchanger drops to 30 K at a nearly constant cooling rate after the startup of the cryocooler. As the charging pressure increases from 2.2 to 2.6 MPa, the cooling rate increases from 16.59 to 19.46 K/min, and the cooling rate increases by about 0.72 K/min for every increase in pressure of 0.1 MPa. Under the charging pressure of 2.6 MPa, the second stage of the cryocooler reaches a no-load refrigeration temperature of 19.83 K, while the temperature of the first stage is 71.2 K. The no-load refrigeration temperature has a weak relationship with the charging pressure. As the charging pressure increases, the increasing rate of cooling capacity and COP with the refrigeration temperature increases. The cryocooler is capable of providing 110 W cooling power at 30 K with a relative Carnot efficiency of 10.96%. This is the best result ever reported in China. What is more, it is found that the cooling power at the two stages has little influence on the cooling performance of each other, which means the cooling power from the first stage can be applied in the pre-cooling process with little influence on the second stage. These results lay a solid foundation for future applications and performance improvement of the cryocooler.

Transient thermal analysis of multilayer pipeline with phase change material

Based on thermal energy storage concept, multilayer composite pipeline with phase change material (PCM) has been proposed recently as an effective method to meet flow assurance challenges in deep water environment by releasing latent heat and extending cool-down time under shut-in condition. This work presents a mathematical model for the start-up and cool-down processes in a multilayer pipeline with an inner steel pipe, an intermediate PCM layer, and an external thermal insulation layer. With enthalpy formulation adopted for the PCM layer, the governing equations for heat conduction in the composite pipe walls and for energy transport in the produced fluid are solved numerically by explicit finite difference methods. The effects of the PCM thickness ratio, the phase change temperature, and the thermal conductivity ratio between the thermal insulation layer and phase change material are investigated. The effect of PCM hysteresis on the transient heat transfer process is also evaluated. It is found that there is an optimal PCM thickness ratio for a given combination of PCM and thermal insulation materials that maximizes the overall cool-down time. The cool-down time and the optimum PCM thickness ratio increase when the phase change temperature decreases. For a given PCM, the optimum PCM thickness ratio decreases for increasing thermal conductivity ratio. There is an interval of thermal conductivity ratio between 0.2 and 0.8 within which the PCM layer with optimum thickness ratio provides a significant increase in the cool-down time.

Unsteady numerical simulation on helium cooldown process for the 650 MHz two-cell superconducting cavity

Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone (4.2 K and below) in the testing and sophisticated operation process of superconducting cavity. The purpose of this paper is to study the cooling law on the helium cooldown process for the 650 MHz two-cell superconducting cavity with the unsteady numerical simulation. A three-dimensional coupled heat-flow model of 650 MHz two-cell superconducting cavity was established. The unsteady numerical simulation of different inlet temperatures, flow rates and pressure conditions was carried out. The equivalent convective heat transfer coefficient and temperature distribution of 650 MHz two-cell superconducting cavity during cooldown process were obtained. The effects of cooling time and entrance parameters on the cooldown process were analyzed. The temperature distribution of the lower intersection lines has a large drop in the initial stage of cooldown process (120 s), while the temperature near the flanges at the both ends is still higher (remaining at the initial temperature of 300 K). With the passage of time, the temperature of the upper and lower intersection lines decreases. The maximum temperature difference on the lower intersections is within 2 K in the final stage of cooldown process (3600 s). The maximum temperature difference increases by 180%, and the difference between the maximum temperature and the minimum temperature (dT) at the end of a cooldown stage increases by 130% after 1 h, respectively, when the inlet temperature drops from 290 to 270 K (under the condition of the initial temperature of 300 K). The maximum temperature difference and the dT at the end of a cooldown stage increase with the decrease in the inlet temperature. The maximum temperature difference increases with the increase in the inlet flow rate, while the dT at the end of a cooldown stage decreases with the increase in the inlet flow rate. The effect of changing the inlet flow rate on the cooling rate is not as obvious as changing the inlet temperature. Once there is a certain flow rate, the advantage of further increasing the flow rate to reduce the temperature of the superconducting cavity is not so great.

Mechanical Modeling and First Case Study on ITER TF CICC Loading Cases With Upgraded Finite Element Code Simulations

The strands of the Cable-In-Conduit Conductors (CICCs) for the ITER magnet system TF coils are made of Nb3Sn, which is a brittle and strain-sensitive superconducting material. The strain distribution in the filaments is driven by the cool-down process and the electromagnetic forces acting on the strands in operation. The impact of electromagnetic and thermal warm-up-cool-down cycles on the conductor performance degradation has been investigated experimentally both on short samples in the SULTAN facility and in the solenoidal configuration of the TF Insert tests in the CSMC facility. A deeper understanding on how cyclic loading of the conductor affects its electrical performance could allow one to identify the best working conditions so as to limit the degradation. In this paper, a mechanical model of one last sub-cable (petal) of the TF CICC is presented. The strain distribution in the strands is simulated via a new version of the MULTIFIL finite element code. The effects of the alternate application of thermal and electromagnetics cyclic loading are tentatively analyzed, similarly to experiments performed in the SULTAN facility in the tests of the TFIO1 conductor sample. An upgrade of the model is implemented, concerning the thermal cycle simulation.

Effect of Hydrogen-Ion-Implantation on Self-Separation of Free-Standing Gallium Nitride Wafers Grown By Hvpe

In recent years, free-standing Gallium Nitride (FS-GaN) wafers were utilized as substrates for high-brightness light-emitting-diodes (HB-LED), LASER diodes (LD) and power devices due to their characteristics, such as 3 times higher thermal conductivity than sapphire substrates and higher breakdown voltage than conventional Si substrates. The FS-GaN wafers grown by hydride vapor phase epitaxy (HVPE) demonstrated lower dislocation density (DD) than that of GaN wafers grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates (template GaN wafer). However, one of big challenges for their commercializing is the crack free FS-GaN wafers during the HVPE GaN growth, which resulted in lowering the productivity and increasing the fabrication cost. The main cause of the cracking is the stress induced by the differences in thermal expansion coefficients (TEC) and lattice constants of sapphire and GaN. To overcome this issue, the design of GaN growth process with self-separation is the key technology. The self-separation technique consists of two key points, one is separation enhancement and the other is blocking edge-poly-GaN growth. In this study, we investigated the effect of hydrogen-ion-implantation on self-separation of FS-GaN wafers. In addition, the blocking effect of edge grinding of template GaN wafers was also investigated. Two-inch-diameter template GaN wafers with the GaN layer thickness of 5 μm were prepared and the hydrogen-ions were implanted with various dose conditions to enhance self-separation of FS-GaN wafers from the sapphires. The edges of the implanted template GaN wafers were then ground to eliminate the polished edge surfaces to deter the poly-GaN growth. 800-μm-thick GaN layers were grown by HVPE on the template GaN wafers, and the FS-GaN wafers were successfully self-separated during the cool-down process. Fig. 1 shows the edge images of the GaN on sapphire substrates after 300-μm-thick GaN layer was grown on the template GaN substrates. When the edge-grinding was utilized to template GaN substrate, the poly-GaN was grown less than that of the substrate without edge-grinding. Also, the poly-GaN was easily removed at the edge of the substrate by edge-grinding without additional process. Fig. 2 shows the hydrogen-ion-band inside the MOCVD-GaN layer with three different hydrogen-ion dose conditions. The sample with hydrogen-ion dose of 2.25 E17 H+/cm2 showed larger size of the hydrogen cavity than the samples with hydrogen-ion dose of 1.75 E17 and 2.0 E17 H+/cm2. Fig. 3 shows the wafer images after 800-μm-thick GaN grown on the edge-ground template GaN with three different hydrogen-ion-implantation conditions. The FS-GaN wafers with hydrogen-ion dose of 1.75 E17 and 2.0 E17 H+/cm2 were successfully self-separated from the sapphire substrates, while the sample with hydrogen-ion-dose of 2.25 E17 H+/cm2 was self-separated around 63% of the area. In our presentation, we will report how we achieved the self-separation of FS-GaN wafers without cracking by hydrogen-ion-implantation into the template GaN substrates, and discuss about the crystal quality of the grown FS-GaN samples. * This work was financially supported by the Brain Korea 21 Plus Program in 2018. Figure 1

Thermal Analysis and Simulation of Cryopump Based on CFD Method

Based on CFD method, thermal design and numerical simulation of cryopump first array and second array was performed during the cool-down period and the steady state. The analysis of the temperature distribution of the cryopump was made under various conditions, such as operating conditions, the setting of the thermal rods and the thickness of the radiation shield. The const thermal property and variable thermal property was used in this paper to calculate the cool-down process of the cryopump, the effect of the first array structure was also taken into account. Some important results with typical parameters are: The temperature difference of the first array of the cryopump is greatly affected by the working conditions, especially when facing the room temperature vacuum system, the main heat load is concentrated on the baffle; A variable thickness bottom plate can be used to reduce the overall temperature change of the cryopump; The setting of the thermal rods is very useful to reduce the temperature change of the cryopump; The setting of the thermal rods is preferably close to the center of the baffle; If the variable property was not considered, the deviation of the cool-down time is about 24%.

Integration and Commissioning of a Full Localization 250 W @ 4.5 K Helium Refrigerator at TIPC

A full Localization 250W@4.5K helium cryogenic refrigerator, composed of a helium screw compressor and its oil-removal subsystem, six plate-fin cryogenic heat exchangers, two high speed turbine expanders, eight pneumatic valves and a vessel with heat load, was developed at TIPC. The high and low pressure can be maintained stable by adjusting the PI parameters of pneumatic valves. Commissioning full localization 250W@4.5K refrigerator system is discussed. 300~4.5K cool-down processes of cryogenic heat exchangers are present. The optimized cooling capacity of this refrigerator system is up to 317W at liquid helium teperature.

Dynamic Process and Validation of a Full Localization 250W@4.5K Large Scale Helium Cryogenic Plants

In this paper, a dynamic process simulation and validation of a full localization 250W@4.5K large scale helium cryogenic plant was set up and studied. The 250W@4.5K helium cryogenic plant was composed of a helium screw compressor and its oil-removal subsystem, six plate-fin cryogenic heat exchangers, two high speed turbine expanders, several pneumatic valves and a liquid helium Dewar with heat load. Numerical models of above critical equipment were individually built up, and then the dynamic process of the 250W@4.5K helium cryogenic plant was developed. In order to improve the simulated accuracy, every cryogenic heat exchanger was divided into a number of zones and the thermo-physical properties of metal changing with the temperature was taking into accounted. The dynamic process of helium screw compressor, the curves of 300~4.5K cool-down processes of heat exchangers and turbine expanders were acquired. Furthermore, the simulated results were compared with the design results and experimental data. It is helpful to make control strategies and to commissioning full localization 250W@4.5K helium cryogenic plant.

Transient characteristics and performances of passive recirculation system for liquid rocket engine precooling

This paper presents a numerical study on the transient cooldown process of liquid rocket engine by a passive recirculation precooling system. An unsteady mathematical model is developed by considering the interaction of heat dissipation from solid structure with the time- and location- dependent two-phase flow, and the predicted values show good agreements with experiments. The results demonstrate the roles of boiling regimes, and reveal distinct thermal and flow characteristics from single pipe cooldown and bleed precooling. The liquid rewetting front propagates along the flow direction in the vertical feed line and the turbopump related horizontal pipes, with the exception that opposite propagation appears in the upward recirculation line and causes inverted axial temperature distributions and faster cooling of exit. In terms of the time for meeting the turbopump operation requirement, large-diameter recirculation line and high liquid level in the ullage discharging condition are advantageous to the precooling of cryogenic pump, while subcooled liquid and high liquid level in liquid discharging condition prolong the cooldown process and are undesirable. The dependence of cooldown time on subcooling degree, relative liquid level and recirculation line diameter can be described by linear, cubic and exponential functions, respectively.

Optimization of the Cool-Down Process for a System of Sintering Furnaces

Abstract Sustainability in manufacturing systems involves the balance of energy, waste, and profit. This article presents a case study in which an industrial sintering process is optimized with respect to production, energy use, and material waste. The analysis proceeds by developing a physics-based furnace model, developing a cost function for optimization, and then considering the implementation costs associated with the solution. The furnace cycle time is reduced by optimally flowing the atmosphere gas through the furnace. A system of furnaces operating continuously is then considered, and the optimal control is modified in order to balance the profits with the implementation costs across a parallel set of furnaces. The implementation costs considered here include (1) the amount of gas storage required and (2) the size of the gas compressor required in order to implement the optimal control solution. The specific modeling and optimization methods used herein have broad application for thermal processes, and the general engineering approach should be used across the manufacturing sector to promote sustainability.

Important interaction of chemicals, microbial biomass and dissolved substrates in the diel hysteresis loop of soil heterotrophic respiration

Increasing the emission of carbon dioxide by heterotrophic respiration (Rh) might lead to global warming. However, issues remain on how Rh responds to changing temperatures, especially with respect to the hysteresis loop in the relationship between Rh and temperature at the daily scale, along with elucidating the underlying mechanisms. We investigated hysteresis loop by measuring Rh in subtropical forest soil at the daily scale (12 h for warm-up (6–30 °C) and cool-down processes (30–6 °C), respectively) using continuous temperature variation and high resolution of measurements over a 56-day incubation period. The ratios of R20 and Q10 between warm-up and cool-down were calculated as the characteristics of diel hysteresis. We measured chemical (pH, conductivity, oxidation-reduction potential), microbial biomass and dissolved substrate (carbon and nitrogen) parameters to explain variation of diel hysteresis. Rh was strongly dependent on temperature, with a clockwise hysteresis loop of Rh between the warm-up and cool-down daily processes. The average value of R20 [at a reference temperature of 20 °C] during the whole incubation period under the warm-up process was significantly higher (46.05 ± 0.96 μgC g−1 d−1) than that under the cool-down process (14.74 ± 0.03 μgC g−1 d−1). In comparison, the average value of Q10 under the cool-down process (5.27 ± 0.2) was significantly higher than that under the warm-up process (1.66 ± 0.02). Redundancy analysis showed that the interaction effects of soil chemical, microbial biomass, and dissolved substrate parameters explain most variation of diel hysteresis: 98% variation in R20 and 93.5% variation in Q10. Compared with the weak effect of chemistry parameters on the diel hysteresis, the sole and interactive effects of microbial biomass and substrate were more important, especially their interaction. Interactions of chemical, microbial biomass, and dissolved substrate parameters dominated the variation in diel hysteresis of Rh with temperature, especially the interaction of microbial biomass and dissolved substrate. Of note, Q10 during the warm-up process might be overestimated when using the highly fitted temperature-dependent function of cool-down period. Furthermore, using a constant value of Q10 (Q10 = 2) in carbon cycle models might be an important source of uncertainty.

An efficient analytical homogenization technique for mechanical-hygrothermal responses of unidirectional composites with applications to optimization and multiscale analyses

The elasticity-based Locally Exact Homogenization Theory (LEHT) is extended to study the mechanical-hygrothermal behaviors of unidirectionally-reinforced composites. Based on the framework developed previously, thermal and moisture effects are incorporated into the LEHT to study the homogenized and localized responses of heterogeneous materials, which are validated using available analytical and numerical techniques. The LEHT programs are then encapsulated as subroutines with Input/Output (I/O) interfaces, to be readily applied in different computational scenarios. In order to illustrate the efficiency of the LEHT, the theory is firstly coupled to the Particle Swarm Optimization (PSO) algorithm in order to minimize the axial thermal expansion mismatch in hexagonal and square fiber arrays by tailoring the fiber volume fraction. The LEHT is then implemented into the lamination theory to study fabrication-induced residual stresses arising during the cool-down process which introduces local laminate stresses owing to thermo-mechanical property mismatch between plies. Both of these applications illustrate the efficiency and accuracy of the LEHT in generating effective properties and local stress distributions, making the theory a golden standard in validating other analytical or numerical techniques as well as a reliable tool in composite design and practice for professionals and non-professionals alike.

Structural Behavior of KSTAR CS Magnet During Plasma Operation

The finite element model of KSTAR central solenoid (CS) magnet has been developed with new smeared orthotropic material properties of CS coils and the effective coefficient of thermal expansion of the magnet structures. The accuracy of structural analysis for assembly and cool-down processes is higher than in previous studies. Electromagnetic analysis was performed to evaluate Lorentz forces of poloidal field (PF) coils during a long pulse discharge. The analyzed structural behavior of the CS magnet was clearly consistent with the measured data and calculated Electromagnetic (EM) forces during the plasma operation. The current of PF4 coil had a significant effect on axial compression and the minimum preloading was maintained at 2.0 MN in the end of plasma. Equivalent EM force can easily predict the axial compression of CS magnet without complicated structural analysis. The study on the structural behavior of CS magnet is expected to provide the optimal combination of PF coil current limits for large plasma current and long pulse discharges.

Solid Rocket Motor Propellant Optimization with Coupled Internal Ballistic–Structural Interaction Approach

This research aims to optimize the geometric design of slotted propellant grains for solid rocket motors with respect to coupled internal ballistic performance and structural strength criteria. In-house codes such as a zero-dimensional internal ballistic solver and an analytical burnback solver are implemented to compute the variation of chamber pressure and the rocket thrust transiently. Structural analysis of the solid propellant is achieved by using a parametric linear viscoelastic model and a parametric cooldown heat transfer model, both of which are based on the finite element method. The transient temperature distribution data derived from the cooldown process are required inputs for the material properties to be used in the viscoelastic structural analysis. To enable an efficient optimization process, a surrogate heat transfer model that predicts the cooldown time of the system by eliminating expensive iterations is also implemented and validated. Within a coupled analysis approach, the pressure data obtained from the internal ballistic performance analysis are used for the ignition step of the linear viscoelastic analysis. The structural analysis results are evaluated by using a deterministic approach based on the margin of safety with respect to the stress and strain criteria. Finally, the optimum geometrical parameters for a slotted grain subjected to both structural and internal ballistic performance constraints are investigated through multidisciplinary optimization techniques.