• Energy Research

This paper studies an absorption machine driven by the heat recovered from a Solid Oxide Fuel Cell (SOFC). The absorption unit was first evaluated by a cycle analysis determining the sensitivity to the main boundary conditions and to the internal parameters. Then a specific simulation code of all the different devices of the absorption machine was developed to evaluate the performance and size of the unit together with its operating condition limits.

This paper studies an absorption machine driven by the heat recovered from a Solid Oxide Fuel Cell (SOFC). The absorption unit was first evaluated by a cycle analysis determining the sensitivity to the main boundary conditions and to the internal parameters. Then a specific simulation code of all the different devices of the absorption machine was developed to evaluate the performance and size of the unit together with its operating condition limits.

Abstract R1233zd(E) has been proposed as low GWP alternative to R245fa. This paper compares the R1233zd(E) and R245fa performance during flow boiling inside a small diameter microfin tube having internal diameter at the fin tip equal to 4.2 mm, 40 fins, 0.15 mm high, and a helix angle of 18°. The experimental measurements were carried out at a constant mean saturation temperature of 30 °C, by varying the refrigerant mass velocity between 100 kg m−2 s−1 and 300 kg m−2 s−1, the mean vapor quality from 0.1 to 0.95, and the heat flux from 15 to 90 kW m−2. The experimental results showed that R1233zd(E) presented almost similar flow boiling heat transfer coefficients at all the investigated mass velocities but slightly higher two-phase frictional pressure drops. The experimental measurements were compared against the calculated values of boiling heat transfer coefficients and frictional pressure drops from several models selected from the open literature.

Abstract R1233zd(E) has been proposed as low GWP alternative to R245fa. This paper compares the R1233zd(E) and R245fa performance during flow boiling inside a small diameter microfin tube having internal diameter at the fin tip equal to 4.2 mm, 40 fins, 0.15 mm high, and a helix angle of 18°. The experimental measurements were carried out at a constant mean saturation temperature of 30 °C, by varying the refrigerant mass velocity between 100 kg m−2 s−1 and 300 kg m−2 s−1, the mean vapor quality from 0.1 to 0.95, and the heat flux from 15 to 90 kW m−2. The experimental results showed that R1233zd(E) presented almost similar flow boiling heat transfer coefficients at all the investigated mass velocities but slightly higher two-phase frictional pressure drops. The experimental measurements were compared against the calculated values of boiling heat transfer coefficients and frictional pressure drops from several models selected from the open literature.

Abstract This paper presents the experimental tests on desiccant regeneration carried out in a packed column with the hygroscopic solution H 2 O/LiBr. Two different packed columns have been tested: a random column consisting of 1” Pall Ring elements and a structured column Mellapack 250Y. The experimental results are reported in terms of desiccant concentration increase, regeneration effectiveness and air side pressure drop. The experimental tests show that desiccant regeneration requires a temperature level around 50 °C that can be easily obtained by using solar energy or heat recovered from an industrial process or from a thermal engine. The random column shows regeneration performance 20–25% higher than structured column, whereas the structured column shows air side pressure drop from 65% to 75% lower. The experimental results have been compared against a one-dimensional simulation code of a packed column: a fair agreement is found between experiments and simulation.

Abstract This paper presents the experimental tests on desiccant regeneration carried out in a packed column with the hygroscopic solution H 2 O/LiBr. Two different packed columns have been tested: a random column consisting of 1” Pall Ring elements and a structured column Mellapack 250Y. The experimental results are reported in terms of desiccant concentration increase, regeneration effectiveness and air side pressure drop. The experimental tests show that desiccant regeneration requires a temperature level around 50 °C that can be easily obtained by using solar energy or heat recovered from an industrial process or from a thermal engine. The random column shows regeneration performance 20–25% higher than structured column, whereas the structured column shows air side pressure drop from 65% to 75% lower. The experimental results have been compared against a one-dimensional simulation code of a packed column: a fair agreement is found between experiments and simulation.

Abstract This paper presents a new computational procedure for refrigerant condensation inside herringbone-type Brazed Plate Heat Exchanger (BPHE). A transition point between gravity controlled and forced convection condensation was found for an equivalent Reynolds number around 1600. At low equivalent Reynolds number ( 1600) the heat transfer coefficients depend on mass flux and condensate drainage is controlled by the combined actions of gravity and vapour shear. A new model was developed for predicting the heat transfer coefficients in the forced convection condensation region. This new model was also applied to super-heated vapour condensation by using the equation of Webb (1998) to account for super-heating effects. The new computational procedure was compared against data from the literature: the mean absolute percentage deviation between experimental and calculated heat transfer coefficients was lower than 16%.

Abstract This paper presents a new computational procedure for refrigerant condensation inside herringbone-type Brazed Plate Heat Exchanger (BPHE). A transition point between gravity controlled and forced convection condensation was found for an equivalent Reynolds number around 1600. At low equivalent Reynolds number ( 1600) the heat transfer coefficients depend on mass flux and condensate drainage is controlled by the combined actions of gravity and vapour shear. A new model was developed for predicting the heat transfer coefficients in the forced convection condensation region. This new model was also applied to super-heated vapour condensation by using the equation of Webb (1998) to account for super-heating effects. The new computational procedure was compared against data from the literature: the mean absolute percentage deviation between experimental and calculated heat transfer coefficients was lower than 16%.