Falling film evaporator

Abstract

Falling film and hybrid falling film evaporators are provided for use in a two-phase refrigeration system or process system. The evaporator includes a shell having an upper portion, a lower portion, and a tube bundle having tubes extending substantially horizontally in the shell. A hood disposed over the tube bundle has an upper end adjacent the upper portion above the tube bundle, the upper end having opposed substantially parallel walls extending toward the lower portion, the walls terminating at an open end opposite the upper end. Once liquid refrigerant or liquid refrigerant and vapor refrigerant is deposited onto the tube bundle, the substantially parallel walls of the hood substantially prevent cross flow of refrigerant vapor or liquid and vapor between the tubes of the tube bundle. A flow distributor disposed adjacent the open end between the hood and the shell modifies the refrigerant flow, providing more uniform refrigerant flow distribution.

1 . A refrigeration system comprising:
 a compressor, a condenser, an expansion device and an evaporator connected in a closed refrigerant loop; and   the evaporator comprising:
 a shell having an upper portion and a lower portion; 
 a tube bundle, the tube bundle having a plurality of tubes extending substantially horizontally in the shell; 
 a hood disposed over the tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being disposed above the tube bundle adjacent the upper portion of the shell, the hood further having opposed substantially parallel walls extending from the closed portion toward the open portion of the shell; 
 a refrigerant distributor disposed below the hood and above the tube bundle, the refrigerant distributor being configured to deposit liquid refrigerant or liquid and vapor refrigerant onto the tube bundle, the substantially parallel walls of the hood substantially prevent cross flow of the refrigerant between the plurality of tubes of the tube bundle; 
 a flow distributor disposed adjacent the open end between the hood and the shell; and 
 wherein the flow distributor modifies the refrigerant flow between the hood and the shell to provide a more uniform refrigerant flow distribution. 
   
   
   
       2 . The refrigerant system of  claim 1  wherein the flow distributor is angled from a hood wall. 
   
   
       3 . The refrigerant system of  claim 2  wherein the flow distributor extends from the hood wall. 
   
   
       4 . The refrigerant system of  claim 2  wherein the flow distributor extends from the shell. 
   
   
       5 . The refrigerant system of  claim 1  wherein the flow distributor is curved. 
   
   
       6 . The refrigerant system of  claim 1  wherein the flow distributor includes a plurality of through apertures. 
   
   
       7 . The refrigerant system of  claim 6  wherein the flow distributor extends between the hood wall and the shell. 
   
   
       8 . A falling film evaporator for use in a refrigeration system comprising:
 a shell having an upper portion and a lower portion;   a tube bundle, the tube bundle having a plurality of tubes extending substantially horizontally in the shell;   a hood disposed over the tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being disposed above the tube bundle adjacent the upper portion of the shell, the hood further having opposed substantially parallel walls extending from the closed portion toward the open portion of the shell;   a refrigerant distributor disposed below the hood and above the tube bundle, the refrigerant distributor being configured to deposit liquid refrigerant or liquid and vapor refrigerant onto the tube bundle, the substantially parallel walls of the hood substantially prevent cross flow of the refrigerant between the plurality of tubes of the tube bundle;   a flow distributor disposed adjacent the open end between the hood and the shell; and   wherein the flow distributor modifies the refrigerant flow between the hood and the shell to provide a more uniform refrigerant flow distribution.   
   
   
       9 . The falling film evaporator of  claim 8  wherein the flow distributor is angled from a hood wall. 
   
   
       10 . The falling film evaporator of  claim 9  wherein the flow distributor extends from the hood wall. 
   
   
       11 . The falling film evaporator of  claim 9  wherein the flow distributor extends from the shell. 
   
   
       12 . The falling film evaporator of  claim 8  wherein the flow distributor is curved. 
   
   
       13 . The falling film evaporator of  claim 8  wherein the flow distributor includes a plurality of through apertures. 
   
   
       14 . The falling film evaporator of  claim 13  wherein the flow distributor extends between the hood wall and the shell. 
   
   
       15 . A hybrid falling film evaporator for use in a refrigeration system comprising:
 a shell having an upper portion and a lower portion;   a lower tube bundle in fluid communication with an upper tube bundle, the lower and upper tube bundles each having a plurality of tubes extending substantially horizontally in the shell, the lower tube bundle being at least partially submerged by refrigerant in the lower portion of the shell;   a hood disposed over the upper tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being adjacent the upper portion of the shell above the upper tube bundle, the hood further having opposed substantially parallel walls extending from the closed end toward the open end adjacent the lower portion of the shell;   a refrigerant distributor, the refrigerant distributor being disposed above the upper tube bundle, the refrigerant distributor depositing refrigerant onto the upper tube bundle;   the substantially parallel walls of the hood substantially preventing cross flow of refrigerant between the plurality of tubes of the upper tube bundle;   a flow distributor disposed adjacent the open end between the hood and the shell; and   wherein the flow distributor modifies the refrigerant flow between the hood and the shell to provide a more uniform refrigerant flow distribution.   
   
   
       16 . The falling film evaporator of  claim 15  wherein the flow distributor is a member angled from a hood wall. 
   
   
       17 . The falling film evaporator of  claim 16  wherein the flow distributor extends from the hood wall. 
   
   
       18 . The falling film evaporator of  claim 16  wherein the flow distributor extends from the shell. 
   
   
       19 . The falling film evaporator of  claim 15  wherein the flow distributor is curved. 
   
   
       20 . The falling film evaporator of  claim 15  wherein the flow distributor includes a plurality of through apertures. 
   
   
       21 . The falling film evaporator of  claim 20  wherein the flow distributor extends between the hood wall and the shell. 
   
   
       22 . A falling film evaporator for use in a control process comprising:
 a shell having an upper portion and a lower portion;   a tube bundle, the tube bundle having a plurality of tubes extending substantially horizontally in the shell;   a hood disposed over the tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being disposed above the tube bundle adjacent the upper portion of the shell, the hood further having opposed substantially parallel walls extending toward the lower portion of the shell;   a fluid distributor disposed below the hood and above the tube bundle, the fluid distributor being configured to deposit liquid fluid or liquid and vapor fluid onto the tube bundle;   the substantially parallel walls of the hood substantially preventing cross flow of the fluid between the plurality of tubes of the tube bundle;   a flow distributor disposed adjacent the open end between the hood and the shell; and   wherein the flow distributor modifies the refrigerant flow between the hood and the shell to provide a more uniform refrigerant flow distribution.   
   
   
       23 . A falling film evaporator for use in a refrigeration system comprising:
 a shell having an upper portion and a lower portion;   a tube bundle, the tube bundle having a plurality of tubes extending substantially horizontally in the shell;   a hood disposed over the tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being disposed above the tube bundle adjacent the upper portion of the shell, the hood further having opposed substantially parallel walls extending from the closed portion toward the open portion of the shell; and   wherein the hood is asymmetrically disposed within the evaporator.   
   
   
       24 . A falling film evaporator for use in a refrigeration system comprising:
 a shell having an upper portion and a lower portion;   a tube bundle, the tube bundle having a plurality of tubes extending substantially horizontally in the shell;   a hood disposed over the tube bundle, the hood having a closed end and an open end opposite the closed end, the closed end being disposed above the tube bundle adjacent the upper portion of the shell, the hood further having opposed substantially parallel walls extending from the closed portion toward the open portion of the shell; and   wherein the hood includes surface textures.   
   
   
       25 . The falling film evaporator of  claim 24  wherein a roof of the hood includes surface discontinuities sufficient to distribute liquid refrigerant therefrom.