Kodi munayamba mwakhalapo pagombe tsiku lowala? Pa tsiku lowala, nthawi zonse pamakhala mphepo yochokera kunyanja kupita kumtunda pagombe. N’chifukwa chiyani nthawi zonse pamakhala mphepo pagombe ndipo n’chifukwa chiyani mphepo ya m’nyanja (mphepo yochokera kunyanja kupita kumtunda) imachitika masana, ndipo mphepo ya kumtunda (mphepo yochokera kumtunda kupita kunyanja) imachitika usiku? N’chifukwa chiyani mitambo imatsika pamapiri nthawi yamvula? N’chifukwa chiyani mphepo imamveka yozizira? Mayankho a mafunso awa akukhudzana ndi kutentha kwa dziko ndi nyanja, kukula, kuchulukana , ndi kusamutsa kutentha pogwiritsa ntchito convection ( kusamutsa kutentha ). Mukamvetsetsa bwino nkhaniyi, mutha kuyankha mafunso omwe ali pamwambapa ndi mafunso ena omwe mungafunse pambuyo pake.
Kusamutsa kutentha kudzera mu conduction nthawi zambiri kumachitika mu zinthu zolimba kapena kuchokera ku zinthu zolimba kupita ku zamadzimadzi (zamadzimadzi kupita ku zinthu zolimba) kapena kuchokera ku zinthu zolimba kupita ku mpweya (mpweya kupita ku zinthu zolimba). Kusamutsa kutentha kwa convection nthawi zambiri kumachitika mu zinthu zamadzimadzi (monga madzi) ndi mpweya (monga mpweya).
Kusamutsa kutentha kwa convection ndi kusamutsa kutentha komwe kumayenderana ndi kuyenda kwa zinthu. Kuti mumvetse bwino kusamutsa kutentha kwa convection, ganizirani chitsanzo, monga madzi omwe amatenthedwa pogwiritsa ntchito moto. Madzi omwe ali mu chidebe akatenthedwa ndi moto, kutentha kumachoka pamoto (kutentha kwakukulu) kupita ku chidebe (kutentha kochepa) pogwiritsa ntchito mphamvu yamagetsi ndi kuwala. Kutentha kumachoka pa chidebe (kutentha kwakukulu) kupita kumadzi omwe ali pafupi ndi chidebe (kutentha kotsika) pogwiritsa ntchito mphamvu yamagetsi. Kutentha kowonjezera kumapangitsa kutentha kwa madzi omwe ali pafupi ndi chidebe kukwera. Kuwonjezeka kwa kutentha kumapangitsa kuti madzi akule, ndikuwonjezera mphamvu yake. Pamene mphamvu ikukwera, mphamvu yake imachepa. Madzi omwe ali pafupi ndi pansi pa chidebe amakhala ndi kutentha kwakukulu kuposa madzi omwe ali pamwamba pake. Mwanjira ina, madzi omwe ali pafupi ndi pansi pa chidebe amakhala ndi mphamvu yayikulu komanso yochepa, pomwe madzi omwe ali pamwamba pake amakhala ndi mphamvu yochepa komanso yochepa. Kusiyana kwa mphamvu kumapangitsa kuti madzi omwe ali pamwamba pa chidebe, omwe ali ndi mphamvu yayikulu, asunthire pansi ndipo madzi omwe ali pafupi ndi pansi pa chidebe, omwe ali ndi mphamvu yochepa, asunthire mmwamba. Izi zimachitika mosalekeza mpaka madzi onse mkati mwake ali ndi kutentha komweko (Ngati mpweya uli ndi mpweya umodzi, madzi omwe ali mu chidebecho adzaphwanyika, omwe amadziwikanso kuti amawira pa kutentha kwa 100 o C).
Kubwera kwa mphepo zapamtunda ndi mphepo zapanyanja kumakhudzanso kusamutsa kutentha kudzera mu conduction ndi convection. Kutentha kwapadera kwa dziko lapansi (kutentha kwa chinthu cholimba) kumakhala kotsika kuposa kwa madzi a m'nyanja, motero dziko lapansi limatentha mofulumira kwambiri likakumana ndi kuwala kwa dzuwa ndipo limazizira mofulumira usiku. Dziko lapansi limatentha mofulumira, kutentha mpweya pamwamba pake (kusuntha kutentha kuchokera kudziko kupita kumlengalenga kudzera mu conduction). Kutentha kwa mpweya womwe umalandira kutentha kowonjezera kumawonjezeka ndipo mpweya umakula. Zotsatira zake, kuchuluka kwa mpweya kumachepa. Mosiyana ndi zimenezi, kutentha kwa madzi a m'nyanja kumakhala kozizira, kotero mpweya pamwamba pa nyanja nawonso ndi wozizira, poyerekeza ndi mpweya pamwamba pa nthaka. Mpweya pamwamba pa nyanja ndi wozizira kwambiri, kotero kuchuluka kwake ndi kwakukulu. Kusiyana kumeneku kwa kuchuluka kwa mpweya kumapangitsa kuti mpweya pamwamba pa nyanja upite kumtunda, kukankhira mpweya pamwamba pake mmwamba. Kutali ndi dziko lapansi, mpweya wochepa umapangidwa chifukwa cha kuchepa kwa mphamvu yokoka ya Dziko Lapansi. Chifukwa kuchuluka kwa mpweya kumachepa, kuthamanga kwa mpweya kumachepanso. Mpweya wotentha pamwamba pa dziko lapansi womwe umakwera mmwamba umazizira chifukwa ukakhala kutali ndi dziko lapansi, mpweya wochepa umakhalapo. Mpweya wozizira umatsikanso pansi, osati pamwamba pa dziko lapansi koma pamwamba pa nyanja, komwe kumakhala kutentha kozizira. Izi zimachitika mosalekeza, zomwe zimapangitsa kuti mpweya utuluke kuchokera kunyanja kupita kumtunda. Mwachidule, mpweya pafupi ndi nyanja umapita kumtunda, mpweya pafupi ndi nthaka umapita mmwamba, ndipo mpweya pamwamba pake umapita pamwamba pa nyanja.
N’chifukwa chiyani utsi nthawi zonse umakwera mmwamba?
Utsi umakwera chifukwa kutentha kwake kumakhala kokwera kuposa mpweya wozungulira. Chifukwa kutentha kwa utsi kumakhala kokwera, voliyumu yake imawonjezeka ndipo kuchuluka kwake kumachepa. Kuchuluka kochepa kwa utsi kumapangitsa kuti utsi ukhale wochepa poyerekeza ndi mpweya wozungulira. Mpweya wozungulira umakankhira utsiwo mmwamba.
N’chifukwa chiyani mitambo imapita pansi nthawi yamvula? Nthawi yamvula, mitambo imakhala ndi nthunzi yambiri yamadzi, zomwe zimawonjezera kuchulukana kwawo. Mitambo yomwe imakhala ndi nthunzi yambiri yamadzi komanso yokhala ndi kuchulukana kwakukulu imapita pansi kupita kumalo komwe mpweya wozungulira uli ndi kuchulukana komweko monga mtambo.
