Condensation of sodium on a micromachined surface for AMTEC

Crowley, Christopher J.; Izenson, Michael G.

doi:10.1063/1.43115

Cited by 10 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At low electric current, however, the condenser wick may be partially exposed as the liquid sodium recedes into the 250-¹m-wide grooves at its surface. 8 In this case, at T cd D 623 K, a liquid tension of as much as ¡1.38 kPa may develop at the L-V interface in the condenser structure. Figure 3 shows a line diagram of the calculatedlocal sodium pressure in a ve-tube, PX-3A-type converteroperatingat T hot D 1123 K and a peak power of 3.7 W e .…”

Section: Circulation Of Sodium Working Fluid and The Capillary Limitmentioning

confidence: 98%

“…A porous Creare-type condenser wick is used to maintain a continuous thin lm of liquid sodium on its surface, effectively re ecting »95% of escaping thermal radiation toward the interior of the converter. 8 The specially shaped longitudinal ns (»2 mm wide) of the Creare-type condenser provide a capillary force an order of magnitude larger than the hydrostatic force at Earth gravity, forcing liquid sodium to spread uniformly on the surface. The small grooves between ns (»250 ¹m wide) facilitate the condensate ow to an underlying felt wick or small capillary space (see insert in Fig.…”

Section: Design and Operation Of Vapor Anode Amtecmentioning

confidence: 99%

See 1 more Smart Citation

Capillary Limit of Evaporator Wick in Alkali Metal Thermal-to-Electric Converters

Tournier

El‐Genk

2002

Journal of Thermophysics and Heat Transfer

View full text Add to dashboard Cite

Vapor anode, multitube alkali metal thermal-to-electric converters are being developed for potential use in space and terrestrial electric power generation. In these converters, the capillary pressure head produced in the evaporator wick circulates the sodium working uid. A two-dimensional, thermal-hydraulic model of the porous evaporator wick and of the liquid sodium return artery is developed and thermally coupled to an integrated model of a ve-beta 0 0 -alumina solid electrolyte (BASE) tube, stainless-steel sodium converter (PX-3A), and an eight-tube, Mo-41%Re sodium converter. Results showed that the capillary limit in the evaporatorwick of the PX-3A converter is reached at zero electrical current, when the thermal input power to the converter exceeds 16 W, or the hot-side temperature exceeds 1136 K. For the Mo-41%Re converter, these values are 22 W and 1150 K, respectively. Before reaching the capillary limit, however, two or more of the following temperature limits occurred in both converters: 1) the TiNi metal-ceramic braze joints' temperature exceeded 1123 K, 2) the evaporator wick surface temperature exceeded 1023 K, or 3) the temperature difference between the cold end of the BASE tubes and the evaporator wick surface was less than +20 K. (16b) and (17) C p = speci c heat, J/kg ¢ K D = thermal conductance, W/m 2 ¢ K F = Faraday's constant, 96,485 C/mol G E = geometric factor for pressure losses in electrode g = gravity acceleration, 9.81 m/s 2 h = enthalpy, J/kg I = electrical current, A K = permeability, Eqs. (16b) and (17), m 2 k = thermal conductivity, W/m ¢ K M = molecular weight of sodium, 23 g/mole P m 00 ev = vaporization mass ux, kg/m 2 ¢ s P m I = sodium ow rate in the converter, kg/s N B = number of beta 00 -alumina solid electrolyte (BASE) tubes P = pressure, Pa P e = electrical power output, W e P sat = sodium saturation pressure, Pa q = area-averaged velocity in wick, m/s Q = conduction heat ow rate, W Q in = input thermal power, W Q rad = net rate of radiant heat loss, Eq. (2), W R c = radius of curvature, m R g = perfect gas constant, 8.314 J/mol ¢ K R L = external load resistance, Ä R p = effective pore radius of evaporator wick, m .Associate Fellow AIAA. r = radial coordinate, m T = temperature, K t = time, s V L = external load voltage, V Vol = volume, m 3 z = axial coordinate, m ® p = vapor volume fraction in porous wick 0 = conduction/advection heat ux, W/m 2 1P = pressure head/drop, Pa 1R i = radial width of numerical mesh, m 1T = temperature margin (T B ¡ T ev ), K 1t = discretization time step, s 1Z j = axial width of numerical mesh, m " = wick volume porosity µ = apex half angle of cone ¹ = dynamic viscosity, kg/m ¢ s ¹ c = cosine of contact angle, R p =R c ½ = density, kg/m 3 ¾ L = liquid surface tension, N/m Â i; j = evaporation coef cient, Eq. (6), a cc .M=2¼ R g T i; j / 1=2 Subscripts/Superscripts a = anode side of BASE B = cold end of BASE tubes c = cathode side of BASE cap = capillary pressure cd = condenser eff = effective ev = evaporator wick surface hot = hot side of co...

show abstract

Section: Circulation Of Sodium Working Fluid and The Capillary Limitmentioning

confidence: 98%

Section: Design and Operation Of Vapor Anode Amtecmentioning

confidence: 99%

Capillary Limit of Evaporator Wick in Alkali Metal Thermal-to-Electric Converters

Tournier

El‐Genk

2002

Journal of Thermophysics and Heat Transfer

View full text Add to dashboard Cite

show abstract

“…The results showed that the higher electric power output and cell conversion efficiency could be obtained by combining materials with geometrical changes for the cell. A number of vapor anode, multi-tube AMTEC cell designs, similar to the PX-series cells have been developed and optimized for improved performance, using an APEAM [1,15,49,[83][84][85][88][89][90]. The main improvements in AMTEC designs are as follows:…”

Section: The Efficiency Enhancement Of Vapor-fed Vapor Anode Multi-mentioning

confidence: 99%

“…Optimizing dimensions and parameters, such as increasing the cell length for given BASE tubes and cell diameter, or optimizing the length and the number of BASE tubes and electrodes, and making condenser temperature vary between 640 and 670 K [89]. Replace the SS mesh pad condenser by a Creare-type condenser to ensure the formation of a continuous film of liquid sodium on its surface for high reflectivity, and thus reduce the parasitic radiation losses to the condenser [90]. For the same electric current (or sodium flow rate), a flat evaporator would reach the capillary limit at higher temperatures and operates at a temperature slightly lower than that of a conical evaporator [85].…”

Section: The Efficiency Enhancement Of Vapor-fed Vapor Anode Multi-mentioning

confidence: 99%

A review on advances in alkali metal thermal to electric converters (AMTECs)

Xiao

Cao

2009

Int. J. Energy Res.

View full text Add to dashboard Cite

SUMMARYThe alkali metal thermal to electric converter (AMTEC) is one of the most promising technologies for direct conversion of thermal energy to electricity and has been receiving attention in the field of energy conversion and utilization in the past several decades. This paper aims to present a comprehensive review of the state of the art in the research and development of the AMTEC, including its working principles and types, historical development and applications, analytical models, working fluids, electrode materials, as well as the performance and efficiency improvement. The current two major problems encountered by the AMTEC, the time-dependent power degradation and relatively low efficiency compared to its theoretical value, are discussed in depth. In addition, a brief comparison of the AMTEC with other direct thermal to electric converters (DTECs), such as the thermoelectrics converter (TEC), thermionics converter, and thermophotovoltaics converter, is given, and combinations of different DTECs to further improve DTECs' power generation and overall conversion efficiency are demonstrated. Future research and development directions and the issues that need to be further investigated are also suggested. It is believed that this comprehensive review will be beneficial to the design, simulation, analysis, performance assessment, and applications of various types of AMTECs.

show abstract

“…In Japan Kyushu University in collaboration with Electrotechnical Laboratory the interest in AMTEC analysis has evolved [35][36]. Creare Inc. has primarily concentrated on evaporator component of AMTEC to enable it operate efficiently [37][38][39].…”

Section: Active Damping Of the Acoustic Resonancesmentioning

confidence: 99%

Summer Research Program - 1998 Summer Faculty Research Program. Volume 3, Phillips Laboratory

Moore¹

1998

View full text Add to dashboard Cite

Condensation of sodium on a micromachined surface for AMTEC

Cited by 10 publications

References 0 publications

Capillary Limit of Evaporator Wick in Alkali Metal Thermal-to-Electric Converters

Capillary Limit of Evaporator Wick in Alkali Metal Thermal-to-Electric Converters

A review on advances in alkali metal thermal to electric converters (AMTECs)

Summer Research Program - 1998 Summer Faculty Research Program. Volume 3, Phillips Laboratory

Contact Info

Product

Resources

About