Aqueous ammonia solution cooling absorption refrigeration driven by fishing boat diesel exhaust heat

A solution cooling absorption（SCA）approach is proposed to modify the aqueous ammonia absorption refrigerat-ion cycle using the strong solution from the absorber to cool the forepart of the absorption in the cycle for reclaiming some portion of absorption heat.As a consequence of raised temperature at the inlet,the strong solution partially boils at the outlet of the solution heat exchanger,and diminishes the thermal heat consumption of the heat source.The calculation results show that the coefficient of performance（COP）of this modified cycle is about 28.3% higher than that of the traditional cycle under typical conditions;while the required heat transfer area of the total heat exchangers of the cycle is somewhat less than that of the traditional one.The capacity of refrigeration with the new absorption cycle is more than doubled in contrast to the adsorption scheme with an identical configuration.It is sufficient to supply a fishing boat the chilling capacity for preservation of fishing products with the modified cycle chiller driven by its diesel engine exhaust.

Effect of solution cooling rate on the microstructure and creep deformation mechanism of a rhenium-free second-generation single crystal superalloy

Various cooling scenarios(water,oil,air and furnace)were employed to study the impacts of the solution cooling rate(SCR)on the microstructure and creep behavior of a novel single-crystal(SX)superalloy.The results showed that the cubic degree and size of theγphases were inversely proportional to the SCR.The creep life first increased and then dropped dramatically with a reduction in the SCR.The creep life of the sample cooled with air cooling(AC)was the highest,up to 144.90 h at 800℃/750 MPa and160.15 h at 1100℃/137 MPa.During creep at 800℃/750 MPa,the improved creep life of the AC sample was mainly attributed to the fine cubicγphases,which decreased the rate ofγ-phase coarsening and favoured plastic deformation by promoting the active movement of dislocations.The AC helped theγphases become rich in Al,Ti and Ta while depleted in Co and Cr,which enhanced its stacking fault energy,thus promoting the formation of dislocation locks.Meanwhile,the largest negative lattice misfit caused by AC induced denserγ/γinterface dislocation networks at 1100℃/137 MPa,which efficiently reduced the minimum creep rate.The calculated average dislocation spacing results indicated that the smallest density of excess dislocations corresponded to the AC sample,proving its greatest creep resistance.Interestingly,the size of the secondaryγphases first decreased and then increased sharply with decreasing SCR during creep at 1100℃/137 MPa,when fine secondaryγphases had a positive role in the blockage of dislocation movement in the matrix.Eventually,the comprehensive SCR effect was explored to provide more guidance in the design of Re-free SX superalloys.

Evolution of γ' precipitates in GH4742 superalloy based on complete forging-heat treatment process

The temperature changes at the rim,1/2 radius,and bore of the turbine disk during the solution treatment were measured.Based on the measured temperature data,solution treatment experiments with different cooling rates(14,51,and 93℃/min)were performed,and the solution temperatures were 1120 and 1080℃.At all three cooling rates,the multimodal size distribution of γ' precipitates was detected,and the size of γ' precipitates is inversely related to the cooling rate.Only the secondary and tertiary γ' precipitates were found at a solution temperature of 1120℃,and the secondary γ' precipitates progressed from spherical(93 and 51℃/min)to flower-like(14℃/min)shape,with the flower-like γ' precipitates regulated by aggregation.At a solution temperature of 1080℃,the γ' precipitates evolve from cuboids(93 and 51℃/min)to irregular shapes(14℃/min).Irregular γ' precipitates are affected by the lattice mismatch between the matrix and the γ' precipitates.