Nozzle Assembly Research Articles

Horticultural Oil Thermotherapy Delivery System for Perennial Specialty Crops: A-Proof-of-Concept and Preliminary Results

HighlightsHorticultural oil thermotherapy sprayer was developed for use in perennial fruit crops.Prototype design included air-shear nozzles to spray at eight customized heights.Field evaluation provided adequate spray coverage.Abstract. Spray drift and residues of synthetic chemicals used in crop pest management are major concerns in agricultural industry. Therefore, exploration of alternative pest management technologies is necessary to minimize lasting pesticide residues without compromising biological efficacy. As such, this study reports the design and evaluation of a new horticultural oil thermotherapy (HOT) application system intended to increase biological efficacy of low-residue horticultural oils through addition of heat. A field-scale system has been constructed to apply thermotherapy onto tree fruit and berry crop canopies. This system uses a custom heating unit to preheat the spray liquid, reaching the nozzles at temperatures up to 99°C depending on application requirement. The spray delivery and temperature profiles generated by the prototyped HOT system were evaluated at three horizontal distances from the nozzle exit (0.6, 1.5, and 2.1 m) using a smart spray analytical system developed by our research group. Typical to tree fruit sprayers, higher spray delivery was collected at 0.6 m distance and trended to decrease with increasing distance from the nozzles. The spray plume temperature also decreased with increasing distance from the nozzle. The prototype was evaluated in a pear orchard providing adequate spray coverage at bottom (75% average at 1.2 m AGL) and middle (53% average at 2.4 m AGL) canopy zones. However, the coverage in the top canopy zone (3.6 m AGL) was less than 8% and will require adjustments to the nozzle assembly. Overall, configuration refinements and calibration adjustments will be required in the prototyped HOT system depending on the crop growth stage and canopy architecture for optimal application efficacy. The developed system, with due optimization, will be critical in providing evidence supporting the feasibility of HOT applications. Keywords: Alternative pest management, Application technology, Horticultural oil, Thermotherapy, Spray efficacy.

Oscillatory and transient flow modes in block nozzle arrangements with a base region

Multi-jet interactions are characterized by a number of shock and expansion waves, formation of turbulent shear layers and subsonic recirculation zones. The problem of the occurrence of unsteady, transient and oscillatory, processes arising in the nozzle devices of rocket engines at different flight modes is discussed. The main flow regimes, the sequence of their change and qualitative patterns of shock-wave structures that arise in each of the regimes are considered. The main emphasis is paid to the causes of occurrence and mechanisms of maintenance of low-frequency oscillations of the base pressure. The regularities of changes in the amplitude-frequency characteristics of oscillations are studied depending on the main parameters of the problem. Areas of existence of oscillatory processes are found, and a search is carried out for the ranges of design parameters, geometric characteristics of nozzle assemblies that provide a non oscillating flow of gas-dynamic processes. Hysteresis phenomena of shock-wave structure at increase or decrease in the reservoir total pressure is observed.

Modulating flow and mixing characteristics of an inclined jet in crossflow at a large backward inclination angle by acoustic excitation

Previous investigations revealed that the backward-inclined jet in crossflow exhibits seemingly lower transverse velocity and turbulence intensity at inclination angles higher than a critical value about 25°, thus resulting in significantly low jet fluid dispersion properties. In this article, the acoustic excitations were applied to a backward-inclined jet in crossflow at an inclination angle higher than the critical value to examine experimentally whether the flow and dispersion characteristics could be improved or not. The flow in the test section of an open-loop wind tunnel was used as the crossflow. A profiled nozzle assembly with a loudspeaker installed in the lower part of it was used to generate the pulsating jet. The instantaneous and time-averaged smoke flow patterns were obtained by the laser-light-sheet assisted flow visualization method. The binary edge detection method was employed to the long-exposure smoke flow images to measure the jet spread width. The turbulence intensities, as well as the Lagrangian integral turbulence time and length scales, were obtained using a hotwire anemometer. The jet-fluid dispersion characteristics were examined using the tracer-gas detection technique. The results revealed that in the domain of jet pulsation intensity and excitation Strouhal number, the pulsed backward-inclined jet in crossflow presented three characteristic flow modes: synchronized oscillating jet, transition, and synchronized shear-layer vortices. The synchronized oscillating jet exhibited violent transverse oscillations due to the high axial jet pulsations induced by the acoustic excitation. The transverse jet width and jet penetration height were enlarged. The turbulence intensities were significantly increased, and the turbulence time and length scales were decreased, therefore led to a significant enhancement in the jet-fluid dispersions and mixing capabilities.

Effects of backward inclination on a pulsed jet in crossflow

The effects of the backward inclination angle on the flow and jet dispersion characteristics of a pulsed jet in crossflow were studied experimentally in an open-loop wind tunnel. The pulsations were created by a loudspeaker which installed at the bottom of a nozzle assembly. The instantaneous and time-averaged flow patterns were obtained using the laser-light sheet assisted smoke flow visualization method. The instantaneous and average velocities, turbulence intensities, integral turbulence time scales were probed using a hot-wire anemometer. The tracer-gas detection technique was applied to examine the fluid dispersion capability of the jet. With excitation, the axial jet pulsations were transferred to transverse oscillations after the jet was deflected by the crossflow. A small jet backward inclination angle could lead to an increase of jet-fluid dispersion and transverse jet spreading width. There existed a critical jet backward inclination angle of 20° at which the jet-fluid dispersion index and transverse jet spreading width attained the maximum values. Arranging the jet backward inclination angle at values smaller than 20° could induce an increase in dispersion of the pulsed jet in crossflow and benefit the industrial applications which required fast and efficient jet-fluid dispersion and mixing. • Jet backward inclination angle presented significant effects on axial mean velocities, turbulence intensities, and dispersion properties. • There existed a critical jet backward inclination angle of 20° at which the jet spreading width and dispersion attain maximum values. • At jet backward inclination angle smaller than critical value, increasing inclination angle could increase jet-fluid dispersion. • At jet backward inclination angle larger than critical value, increasing inclination angle would significantly decrease jet-fluid dispersion. • Arranging jet backward inclination angle at critical value could benefit industrial applications.

Research and Design of Pipe Cleaning Device with Self-Rotation

Background: With more and more blockages in the drainage pipe, recent patents on the design of the pipe cleaning device are also being addressed increasingly. But the current pipe cleaning device has only a single dredging function, and due to the inefficiency of the nozzle head, it cannot be used for cleaning of the seriously blocked pipelines. Objective: In order to solve these problems, a novel pipe cleaning device with self-rotation is proposed and the fluid simulation analysis is adopted for the low-efficiency problem of the nozzle head in this paper. Methods: Firstly, the overall structure of the drainage pipeline cleaning device was designed. Secondly, the size of the nozzle and the nozzle head was determined. Thirdly, the fluid simulation analysis of the nozzle head was carried out to realize the optimal design of the nozzle head. Finally, according to the above design, a prototype was manufactured. Results: This paper presents a novel pipe cleaning device with self-rotation, which is different from current patents. It is divided into the nozzle head system, walking system, cleaning system, threedimensional modeling and assembly of the above three mechanical systems. The simulation results demonstrated that if a deflector is not fixed inside the nozzle head, the pressure of the nozzle head is about 8542751.89Pa, and the flow rate at the outlet of the nozzle head is 354.897m/s. If a deflector is fixed, the corresponding data is 1.32e + 008Pa and 446.336m/s. The result shows that the proposed new nozzle head optimization is effective. Conclusion: The new design solves the problems of the current patents on pipe cleaning device, and solves the key technical problems of inconvenient cleaning of pipe blockage and low efficiency nozzle head under complex working conditions. As a whole, this paper provides new ideas and new methods for the efficient work of pipe cleaning device and the removal of hard dirt on the inner wall of the pipeline.

Study of efficiency of application of locally reinforced fitting units with stiffening ribs

In this work, one of the main methods of strengthening the hole in the apparatus is considered - strengthening with overhead rings, the advantages and disadvantages of using reinforcing rings are indicated. An analysis of the main methods of strengthening the openings of pressure vessels and devices shows that the difficulties in designing and installing the reinforcing rings are in the technology of assembly, detection of weld defects and detection of the local location of this defect. The work shows the possibilities of using locally rib-reinforced nozzle assemblies, which in some cases can serve as an alternative to reinforcing rings, and are also more technological in manufacture, repair and control. Calculations show that the use of two stiffening ribs oriented along the generatrix of the shell to strengthen the hole allows reducing stresses in the area of welding of the nozzle to the body of the apparatus under static load. Practical experiments carried out at the same time showed that in conditions of dynamic loading, it is categorically not recommended to use the strengthening of the nozzle with local stiffening ribs oriented along the generatrix of the shell.

Variable-geometry nozzle for surface quality enhancement in 3D concrete printing

The 3D Concrete Printing technology (3DCP) has developed fast in the past few years. Compared to conventional construction method, the 3DCP technology offers an advantage in speed and cost. However, the surface of a structure from 3DCP technology requires post-finishing processes as the direct outcome suffers from low quality surface finish problem, such as jagged surface and staircase effect. This study aims to improve the surface finish quality in 3DCP using a developed novel variable-geometry nozzle that can directly control the extrudate geometry during the printing process at every layer. The nozzle assembly features an adjustable nozzle outlet geometry that can be controlled along the process. The mechanism requires a slicing algorithm to determine the extrudate geometry at every layer based on the designated printed structure. The corresponding algorithm was also developed and will be presented in this paper. Subsequently, the functionality of the proposed method was validated with a case study of manufacturing a structure with curved outer-surface geometry (an arch).

Interpretation and application of the hydro-abrasive erosion model from IEC 62364 (2013) for Pelton turbines

Abstract An accurate prediction of hydro-abrasive erosion helps in design, planning and operation strategies of a hydropower plant. In the empirical erosion model from the International Electrotechnical Commission (IEC) 62364 standard, various terms such as flow co-efficient (Kf), material factor (Km) and exponent (p) were not provided for Pelton turbines components. The present paper aims to find the values of these terms and to interpret inadequately defined terms like erosion depth (S) and shape factor (Kshape) for application of IEC 62364 (2013)# model. From some field and laboratory data, the values of Kf and p were obtained for Pelton turbine components using multivariate regression analysis. The obtained values of Kf are in the order of 10−6 and 10−12 for various zones of buckets and nozzle assembly respectively whereas p values are in range 1–5. The Km values for 6 different materials, i.e. three types of chrome nickel steels, plasma and high velocity oxygen fuel (HVOF) sprayed coatings and bronze buckets were obtained as 1, 1, 1, 0.6, 0.1 and 2.2, respectively. #IEC 62364 (2013). Hydraulic machines - Guide for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines. Edition 1.0 (June 2013), International Electro technical Commission, Geneva, Switzerland.

Computational Fluid Dynamics Model of Various Types of Rocket Engine Nozzles

The nozzle is an element of the rocket engine in which the potential energy of gases generated during combustion is converted into the kinetic energy of the gas flow. The design parameters of the nozzle have a decisive influence on the ballistic characteristics of the engine. Designing a nozzle assembly is therefore one of the most responsible stages in developing a rocket engine design. The paper presents the results of the simulation of three types of rocket propulsion nozzles. Calculations were made using CFD (Computational Fluid Dynamics) in ANSYS Fluent software. The analyzed types of nozzles differ in shape. The analysis referred to conical nozzle, a bell type nozzle with a conical supersonic part and a bell type nozzle. Calculation results are presented as pressure, velocity, turbulence kinetic energy and eddy viscosity distributions in the longitudinal section. The results show that the cone nozzle generates strong turbulence in the critical section, which negatively affects the flow of the working gas. In the case of a bell nozzle, the transformation of the wall caused the elimination of flow disturbances in the critical section, which reduced the probability of waves that can form before or after the trailing edge. The most sophisticated construction, the bell-type nozzle, allows for maximizing performance without adding extra weight. The bell type nozzle can be used as a starter and auxiliary engine nozzle due to its advantages.

Spraying of a powder coating on an inner body of a nozzle assembly using a detonation method

Objective. Determining of heat treatment influence on a thermal blanket persistency and geometrical dimensions of its parts.Methods of research. Metallographical surface evaluations of a work-hardened parts geometrical measurements, measuring the adhesion.Results. The article details a detonation spraying of a metal powder coating using condensed high-energy materials based on engineered installation. Results of derived thermal blanket are featured.Scientific novelty. Scientific novelty. Behavior patterns of inner bodyof a nozzle assembly was established. It was identified that heat processing leads to changes in metallurgical structure in an anti-abrasion coating. It was defined that heat processing results in no cracks, cleavages or swellings.В ходе работы была проведена серия постановочных экспериментов по определению влияния термообработки (ТО) теплозащитного покрытия ТЗП-2 на стойкость покрытия. Сравнительные исследования проводились на 2 корпусах внутренних сопловых аппаратов (СА). Выбран оптимальный режим термической обработки.Practical value. During work the series of raising experiments were conducted on determination of influence of heat treatment (HT) of heatcover coverage of HCC-2 on firmness of coverage and geometrical sizes of details. Comparative researches were conducted on 2 corps of internal nozzle vehicles (NV). Optimal heat treatment conditions were established.

Bicomponent nanofibers from core–shell nozzle in gas jet spinning process

ABSTRACTThis work evaluates the use of a core–shell nozzle assembly in conjunction with gas jet spinning technique for production of bicomponent nanofibers from an immiscible polymer pair of polyvinylpyrrolidone (PVP) and poly(vinyl acetate) (PVAc) with three morphological forms—interpenetrating network (IPN), core–shell, and bilobal structurers—by varying the sets of miscible solvents offering different affinity for the polymers. Such fiber structures have strong potential in drug delivery and wound dressing applications. Solutions of PVP and PVAc in respective single solvents metered through a core–shell nozzle assembly meet at the exit of the nozzle and a liquid jet is initiated upon contact with a turbulent gas jet. The gas jet stretches the liquid jet into nanofibers. The results indicate that miscible solvent pairs with low affinity for one of the polymer component yield core–shell morphology with distinct polymer interfaces, while the miscible solvent pairs with high affinity for both polymers produce IPN morphology. Also, interchanging core and shell solutions does not alter the IPN morphology. Finally, bilobal nanofiber structures result from spinning of polymer solutions in miscible solvents with low affinity for the second polymer using a nonconcentric core–shell nozzle assembly. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48901.

ИЗГОТОВЛЕНИЕ ЭКСПЕРИМЕНТАЛЬНОГО КОНСТРУКТИВНО-ПОДОБНОГО ОБРАЗЦА СЕКТОРА СОПЛОВОГО АППАРАТА И ПРОВЕДЕНИЕ ЕГО ИСПЫТАНИЙ ПРИ ТЕМПЕРАТУРЕ 1500 °С

The interaction of the SiC–SiCw–B4C–AlN system ceramic composite material (CCM) with the EP648 alloy in the process of high-temperature brazing was studied. The smallest erosion activity both in relation to CCM, and to the EP648 alloy, has HMP solder VPr50. An experimental constructionally similar sample of the nozzle assembly sector was made using uncooled nozzle blade prototypes from CCM. Tests of an experimental constructionally similar sample of the nozzle assembly sector at a temperature of 1500 °C were carried out. No traces of material ablation from the surface of the CMC were found.

Design of a Continuous Pellet Fueling System for Wendelstein 7-X

A continuous pellet fueling system (CPFS) is currently being designed at the Oak Ridge National Laboratory (ORNL) for the long pulse operation of the Wendelstein 7-X (W7-X) stellarator. The purpose of the CPFS is to provide deep continuous fueling for feedback-controlled high-density operation and mitigation of predicted hollow density profiles. The system will provide the capability to inject cylindrical pellets of solid hydrogen or deuterium into the plasma core, with flexibility to vary the pellet size, velocity, and injection frequency. Pellets are nominally of 3 mm in diameter and have a length between 1 and 4 mm. The heart of the CPFS is a vertically oriented, twin-screw extruder, cooled by three Gifford-McMahon cryocoolers in parallel, designed to form a continuous filament of hydrogen or deuterium. The filament width, which determines the pellet length, can be adjusted by means of a variable nozzle driven by a linear actuator at the base of the extruder. Coupled to the nozzle is a solenoid-operated gas gun and cutter assembly. A pneumatic propellant valve pulses a burst of ~60 bar helium to accelerate the cut pellet into W7-X. Three gaps in the guide tubes provide pumping locations to remove the helium propellant before it reaches the plasma. The maximum velocity of the pellet is limited by its ability to survive navigating the guide tube trajectory intact. A microwave cavity located within the guide tube provides the capability to measure the pellet size and velocity. The mechanical and thermal designs of the W7-X extruder, adjustable nozzle, and gun and cutter assembly design are described. A guide tube design and experimental pellet survivability test results are presented.

Computational Fluid Dynamic Analyses of Flow and Combustion in a Domestic Liquified Petroleum Gas Cookstove Burner—Part I: Design Optimization of Mixing Tube–Burner Assembly

Abstract Liquefied petroleum gas (LPG) is commonly used in domestic kitchen due to its low health and environmental impacts and high heat content compared to other traditional fuels. The growing demand of LPG, notwithstanding its limited reserve, influences the need for performance improvement of the LPG cookstoves. In an LPG cookstove, the fuel–air mixture is prepared in a self-aspirated burner, and burns as a rich premixed flame above the burner. The fuel–air ratio of the reactant mixture influences the burning characteristics and thermal efficiency of the cookstove. This part of work deals with a numerical study of flow and mixing characteristics in the mixing tube and burner assembly of a domestic LPG cookstove. The fuel is injected axially through a narrow nozzle inside the mixing tube causing entrainment of ambient air through the side ports and the end port. The effects of different side-port geometry, nozzle position, inlet fuel pressure, and nozzle throat diameter on the air ingress have been systematically investigated, and the optimum design has been identified. Results of the study provide important information on the design of the practical nozzle and mixing tube assembly of high-efficiency LPG stoves.

Thermal performance enhancement of non-premixed syngas combustion in a partial combustion unit by winged nozzle: Experimental and CFD study

This paper presents the effect of nozzle assembly design on the performance of a partial combustion unit (PCU) using the scale-adaptive simulation (SAS) and non-intrusive laser measurement techniques. Four different configurations were tested, namely, nozzle without wing and three nozzles with wing, i.e., flat surface wing, semi-sphere hollow wing and bent wingtip. The syngas-oxygen reaction chemistry was calculated using non-premixed flame model incorporated with GRI-MECH 3.0 mechanism. The radiative heat transfer was modelled using the discrete ordinates (DO) model. The simulation was compared with the particle image velocimetry (PIV) and a two-dimensional laser doppler anemometry (LDA) measurement on a scaled-down PCU model. A good agreement between the SAS prediction and experimental measurement was obtained. It was found that the modified nozzle assembly design with a semi-sphere hollow wing yielded the highest combustion temperature owing to the intense turbulence-induced recirculation mixing of oxy-fuel. The modified nozzle assembly design introduced in this work increased the peak outlet combustion temperature up to 18% higher compared to the original design. The finding in this work may useful for design retrofits of a combustion system.

High-repetition-rate ( kHz) targets and optics from liquid microjets for high-intensity laser–plasma interactions

High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications. Unfortunately, the high repetition rate and high average power requirements for many applications are not satisfied by the lasers, optics, targets, and diagnostics currently employed. Here, we aim to address the need for high-repetition-rate targets and optics through the use of liquids. A novel nozzle assembly is used to generate high-velocity, laminar-flowing liquid microjets which are compatible with a low-vacuum environment, generate little to no debris, and exhibit precise positional and dimensional tolerances. Jets, droplets, submicron-thick sheets, and other exotic configurations are characterized with pump–probe shadowgraphy to evaluate their use as targets. To demonstrate a high-repetition-rate, consumable, liquid optical element, we present a plasma mirror created by a submicron-thick liquid sheet. This plasma mirror provides etalon-like anti-reflection properties in the low field of 0.1% and high reflectivity as a plasma, 69%, at a repetition rate of 1 kHz. Practical considerations of fluid compatibility, in-vacuum operation, and estimates of maximum repetition rate are addressed. The targets and optics presented here demonstrate a potential technique for enabling the operation of laser–plasma interactions at high repetition rates.

New Measures for Prolonging the Nozzle Service Life

Microstructures of 27SiMnMoVA steel intended for nozzle in raw, as-brazed and as-normalized states were surveyed by using OLS4000 laser scanning confocal microscope, Axiovert-25CA optical microscope and QUENTA-400 scanning electron microscopy. It is found that the microstructures of raw 27SiMnMoVA steel are ferrite and pearlite; the microstructures of the as-brazed 27SiMnMoVA steel are ferrite, martensite, bainite and troostite; the microstructures of as-normalized 27SiMnMoVA steel are sorbite and bainite; and that the as-normalized microstructures are appreciably finer than the as-brazed microstructures. Adjusting the carburizing and hardening processes, a cryptocrystalline martensite provided with better wear-resistance is obtained in the case of 27SiMnMoVA steel specimen, and the effective hardened depth is increased from 0.48mm to 0.75mm. Retained austenite content and wear-resistance of the 27SiMnMoVA steel specimens in different heat treatment conditions were measured by means of D8 Advance X-ray diffractometer and MM200 Pin-on-Disk wear testing machine. The results show that the retained austenite contents in the specimens are six to eight percent, and the abrasion marks are as about 3mm. The volume and superficial area of the cooling chamber were increased by 13% and 23% respectively by the way of improving it’s structure, which made the cooling performance of the needle nozzle enhanced significantly. The purpose of increasing the flow coefficient of the nozzle spray holes, improving the spray quality and performance of the nozzle and prolonging the nozzle assembly service life were achieved by adopting liquid extrusion grinding process and carried out the liquid extrusion grinding in spray holes of the nozzle by using KYM-2 liquid extrusion grinder.

Testing of a Long-Burning-Time Paraffin-Based Hybrid Rocket Motor

One of the main issues that prevents the widespread use of hybrid propulsion is the low regression rate of classical hybrid fuels. Recently, paraffin-based fuels have been proposed as a viable solution; however, concerns about paraffin thermomechanical properties have often been seen as a possible showstopper. A small-scale hybrid rocket, able to burn hydrogen peroxide and paraffin wax for an extended time, has been designed, built, and tested in order to investigate the suitability of paraffin wax as a hybrid fuel for actual missions. The motor has a nominal burning time of 80 s, which is compatible with the majority of the missions performed by rocket motors. The motor has been tested successfully, demonstrating that paraffin can be used on real missions. Two different types of paraffin were used: type A and type B, which have regression rates of 1.45 and , respectively, at a reference oxidizer mass flux of and at a reference pressure of 15 bar. Moreover, temperature measurements inside the fuel grain demonstrated the liquid layer theory to be valid. An instrumented nozzle has also been used to better investigate the thermal behavior of the nozzle assembly.

Understanding Cold Spray for Enhanced Manufacturing Sustainability

High pressure cold spray has been showing increasing promise and application for structural repairs and coating applications where wrought like strengths are required. For example, numerous applications have been developed for repairing high cost and long lead time parts for the aerospace and defense market, such as aircraft skin panels, titanium hydraulic lines, aluminum valve actuator internal bores, hardened and chromed steel shafts, gas turbine engine parts, magnesium castings, and many more. These processes also have direct application in commercial markets like transportation and heavy industry. In particular, parts with lead times in excess of 12 months have been successfully repaired and re-introduced into service. This saves not only the direct cost of the part, but also returns the system to service much sooner. Additional benefits of field application with a hand-held nozzle assembly are also possible, particularly for power plants, refineries, and other large industrial plant operations. Cold spray consequently has a tremendous opportunity to enhance manufacturing sustainability by repairing parts that previously could only be replaced and recycled. It is environmentally friendly, as there are no toxic fumes or other harmful emissions from cold spray. Furthermore, because parts are being repaired and refurbished rather than replaced, there is tremendous cost, energy, and overall environmental benefit, making cold spray a “green” technology and an excellent technology for enhancing the long-term sustainability of high value assets.

Measurement and modeling of filament temperature distribution in the standoff gap between nozzle and bed in polymer-based additive manufacturing

Dispensing of a polymer filament above its glass transition temperature is a critical step in several polymer-based additive manufacturing techniques. While the nozzle assembly heats up the filament prior to dispense, it is important to minimize cooling down of the filament in the standoff distance between the nozzle tip and bed. While heat transfer processes within the nozzle assembly, such as filament melting, and on the bed, such as thermally-driven filament-to-filament adhesion, have been well studied, there is a lack of work on heat transfer in the filament in the standoff region. This paper presents infrared thermography based measurement of temperature distribution in the filament in the standoff region, and an analytical model for heat transfer in this region. The analytical model, based on a balance between thermal advection and convective/radiative heat loss predicts an exponentially decaying temperature distribution, the nature of which is governed by the characteristic length, a parameter that combines multiple process parameters such as mass flowrate, filament diameter, heat capacity and cooling conditions. Experimental data in a wide range of process parameters are found to be in very good agreement with the analytical model. The thermal design space for ensuring minimal temperature drop in the standoff region is explored based on the analytical model. Experimental data and theoretical modeling presented here improve our fundamental understanding of heat transfer in polymer additive manufacturing, and may contribute towards design tools for thermal optimization of these processes.