| dc.contributor.author | Taherian, Hessam. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:40Z | |
| dc.date.available | 1998 | |
| dc.date.issued | 1998 | en_US |
| dc.identifier.other | AAINQ31535 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55552 | |
| dc.description | Natural convection heat transfer was studied in shell-and-coil heat exchangers. One or more helical coils were installed in a cylindrical shell to form a natural convection shell-and-coil heat exchanger. A heated aqueous solution of 40% propylene glycol was pumped through the coils. Water from a storage tank circulated naturally on the shell side of the heat exchanger. The helical coils were made of copper tubes of 4.76, 6.35, 7.94 and 9.52 mm outer diameter. Coil outer diameter was varied from 35.7 to 74.5 mm and coil pitch from 1.00 to 5.96 tube diameters. Two shell diameters of 51 and 77 mm were tested and the shell height was either 382 or 762 mm. Experiments were conducted for glycol mass flow rates from 0.00185 to 0.0343 kg/s and heat transfer rates from 160 to 2300 W. | en_US |
| dc.description | The effects of tube diameter, coil diameter, coil pitch, shell diameter and shell height on the shell-side heat transfer coefficient were studied. Axial temperature profiles in the heat exchangers were analyzed. The shell-side heat transfer coefficient decreased with increasing coil surface area. The optimum dimensionless pitch for the coils was found to be in the range, 1.25 $\leq P\leq$ 1.80. Tube diameter had little influence on the shell-side heat transfer coefficient. Increasing the height of the heat exchanger slightly increased the shell-side heat transfer coefficient. The heat exchanger hydraulic diameter was the most appropriate characteristic length for the Nu-Ra correlations. The Nusselt number was correlated well with the modified Rayleigh number based on the heat exchanger hydraulic diameter by $Nu\sb{Dhx} = 0.182Ra\sbsp{Dhx}{*}\sp{0.394}$ for $2\times10\sp3\leq Ra\sbsp{Dhx}{*}\leq2\times10\sp7$. The Nusselt number was also correlated well with the heat-rate Rayleigh number based on the heat exchanger hydraulic diameter by, $Nu\sb{Dhx} = 0.139Ra\sb{q,Dhx}\sp{0.293}$ for $6\times10\sp4\leq Ra\sb{q,Dhx}\leq2\times10\sp $. The UA product (the overall heat transfer coefficient multiplied by the heat transfer area) of the heat exchangers was not directly proportional to the coil surface area, but varied as $UA\propto A\sp{0.67}$. The largest coil in the triple-coil configurations had heat transfer coefficients 46% less than the values for the single-coil configuration. Suggestions were made to improve the performance of the heat exchangers. The optimum configuration for the shell-and-coil natural convection heat exchanger was discussed. Design and rating procedures were proposed for the heat exchangers. | en_US |
| dc.description | Thesis (Ph.D.)--DalTech - Dalhousie University (Canada), 1998. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Engineering, Mechanical. | en_US |
| dc.title | Natural convection heat transfer in heat exchangers with vertical helical coils. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
