The use of high temperature heat exchangers to increase power plant thermal efficiency

Smyth, R.

doi:10.1109/iecec.1997.656676

Cited by 7 publications

(4 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ceramic materials are an excellent alternative because they can withstand temperatures of 1500-2500°C [14][15][16][17]. Heat exchanger designs using ceramic materials have been developed for solar receivers [18], coal or oil fired steam turbines [16] and hydrogen production from sulfuric acid [15,[19][20][21]. The prior work has focused on silicon carbide (SiC) due to its high mechanical strength (tensile strength of 250 MPa at 1500°C), low coefficient of thermal expansion (5.5 Â 10 À6 K À1 ), and high thermal conductivity ($25 W m À1 K À1 at 1500°C) as compared to other ceramics [16,22].…”

Section: Introductionmentioning

confidence: 99%

“…Heat exchanger designs using ceramic materials have been developed for solar receivers [18], coal or oil fired steam turbines [16] and hydrogen production from sulfuric acid [15,[19][20][21]. The prior work has focused on silicon carbide (SiC) due to its high mechanical strength (tensile strength of 250 MPa at 1500°C), low coefficient of thermal expansion (5.5 Â 10 À6 K À1 ), and high thermal conductivity ($25 W m À1 K À1 at 1500°C) as compared to other ceramics [16,22]. However, SiC oxidizes at the conditions anticipated in a reactor for reduction and oxidation of ceria [23][24][25] and has been observed to react vigorously with ceria at high temperatures [26].…”

Section: Introductionmentioning

confidence: 99%

“…While metals provide high thermal conductivity, the long-term service temperatures of even superalloys are no more than 950°C due to corrosion and the onset of creep [14,15]. Ceramic materials are an excellent alternative because they can withstand temperatures of 1500-2500°C [14][15][16][17]. Heat exchanger designs using ceramic materials have been developed for solar receivers [18], coal or oil fired steam turbines [16] and hydrogen production from sulfuric acid [15,[19][20][21].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Model of an integrated solar thermochemical reactor/reticulated ceramic foam heat exchanger for gas-phase heat recovery

Chandran

Smith

Davidson

2015

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

a b s t r a c tThe efficiency of solar thermochemical cycles to split water and carbon dioxide depends in large part on highly effective gas phase heat recovery. To accomplish this goal, we present the design and analysis of the thermal and hydrodynamic performance of a counter-flow, tube-in-tube alumina heat exchanger operating at temperatures of 1500°C and integrated with a solar thermochemical reactor for isothermal production of syngas via the ceria redox cycle. The heat exchanger tubes are filled with alumina reticulated ceramic to enhance heat transfer. The effects of foam morphology and heat exchanger size on heat transfer, pressure drop, and process solar-to-fuel efficiency are explored by coupling a computational fluid dynamic model of the heat exchanger, including radiative transport, with the overall reactor energy balance. We examine foam pore densities of 10, 20 and 30 PPI, and porosities of 65-90%. The 10 PPI foam yields the best heat transfer performance and lowest pressure drop, as the larger pores enhance radiative heat transfer and decrease fluid phase drag forces. Although lower porosity is preferred to improve solid phase conduction in the RPC, the tradeoff in heat transfer and pressure drop point to use of higher porosity foam. Optimization for solar-to-fuel reactor efficiency is achieved with 85-90% porosity, 10 PPI RPC.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Model of an integrated solar thermochemical reactor/reticulated ceramic foam heat exchanger for gas-phase heat recovery

Chandran

Smith

Davidson

2015

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

show abstract

“…Traditional composite materials have found widespread use for improving cost, weight, size, surface condition, strength, thermal and electrical conduction, etc. [33][34][35][36][37][38][39][40][41][42][43] In this context, leaf-like biomimetic composites can serve an important template for thermal material design especially since by changing the arrangements of the fibers, the properties of the material can be tailored to meet the requirements of a specific application. In addition, leaf-like composite can be used in the design of various sensors by properly controlling temperature of various veins.…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity of biomimetic leaf composite

Liu

Ghosh

Mousanezhad

et al. 2017

Journal of Composite Materials

View full text Add to dashboard Cite

The venous morphology of a typical plant leaf affects its mechanical and thermal properties. Such a material could be considered as a fiber reinforced composite structure where the veins and the rest of the leaf are considered as two materials having highly contrast mechanical and thermal properties. The variegated venations found in nature is idealized into three principal fibers—the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary veins of a typical leaf. This paper addresses the in-plane thermal conductivity of such a composite by considering such a venous fiber morphology embedded in a matrix material. We have considered two cases, fibers having either higher or lower conductivity respect to the matrix. The tertiary fibers do not interconnect the secondary fibers in our present study. We carry out finite element based computational investigation of the thermal conductivity of these composites under uniaxial thermal gradients and study the effect of different fiber architectures. To this end, we use two broad types of architectures both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions are kept constant and a comparative parametric study is carried out by varying the inclination of the secondary fibers. We find the heat conductivity in the direction of the main fiber (Y direction) increases significantly as the fiber angle of the secondary increases. Furthermore, for composite with metal fibers, the conductivity in the Y direction is further enhanced when composite is manufactured by having secondary fibers forming a closed cell structure. However, for composite with ceramic fibers, the conductivity of the composite in the Y direction is little affected by having secondary fibers closed. An opposite behavior is observed when considering conductivity of the composite in the X direction. The conductivity of the composite in the X direction is reduced with increase in the angle of the secondary fibers. Higher conductivity in the X direction is achieved for composite with no closed cells for composites with metal fibers. The results also indicate that for composites with the constant fiber volume fraction, morphology of tertiary fibers may not significantly alter material conductivities. In conclusion, introducing a leaf-mimicking topology in fiber architecture can provide significant additional degrees of tunability in design of these composite structures.

show abstract