B737-300 CREW WAS UNABLE TO COOL THE COCKPIT PROPERLY INFLT.

Narrative

MY CREW ORIGINATED AN AIRPLANE THAT HAD BEEN IDLE IN BNA. THE ACFT WAS VERY WARM AND THE COCKPIT DID NOT COOL EVEN AFTER START; TAXI AND TKOF. OUT OF 1000 FT WE PLACED PACKS TO HIGH/FULL COLD. AFTER LEVEL OFF (30-40 MINS INTO FLT) THE 'A' FLT ATTENDANT CAME INTO THE COCKPIT FOR DRINK SVC AND REMARKED THAT THE COCKPIT WAS EXTREMELY WARM. (MY FO AND I HAD BEEN DISCUSSING THAT FACT. I ESTIMATE THE TEMP WAS 90-100 DEGS F. WE WERE DOING ALL WE COULD TO COOL THINGS; BUT NOTHING SEEMED TO HELP). THERE WAS A NOTICEABLE INFLUX OF COOL AIR WHEN THE FLT ATTENDANT OPENED THE DOOR. AFTER FURTHER DISCUSSION WITH MY FO; I ASKED THE FLT ATTENDANT TO KEEP THE DOOR OPEN AS HE PREPARED HIS DRINK TRAY AND TO BE EXTRA VIGILANT AS HE STOOD IN THE GALLEY. I LEFT THE SEAT BELT SIGN ON TO MINIMIZE PAX MOVEMENT IN THE CABIN. WHEN THE 'A' FLT ATTENDANT HAD HIS DRINK TRAY READY TO SERVE; I ASKED HIM TO SHUT THE DOOR. THE DOOR HAD BEEN OPEN 4-5 MINS. WHEN HE CAME BACK TO PREPARE ANOTHER TRAY; I AGAIN ASKED HIM TO OPEN THE DOOR. AT THAT TIME ONE OF THE OTHER FLT ATTENDANTS ENTERED THE COCKPIT AND EXPRESSED CONCERN THAT THE DOOR WAS OPEN. I EXPLAINED OUR ACTIONS. SHE WAS STILL CONCERNED; SO I SHUT THE DOOR. MY DECISION TO OPEN THE DOOR WAS MADE ONLY AFTER SERIOUS THOUGHT AND DISCUSSION WITH MY FO. I FELT IT WAS OUR BEST OPTION FOR REMEDYING A VERY UNCOMFORTABLE SIT. AT ALL TIMES THE OPEN DOOR WAS WATCHED BY THE FLT ATTENDANT IN THE FORWARD GALLEY. WE CONTINUED TO SAT AND TERMINATED THE AIRPLANE. I SHOULD HAVE WRITTEN UP THE AIRPLANE THEN; BUT FAILED TO DO SO.