260
R. Saxena et al.
conditions in India. PCMs showed better results in terms of temperature reduction
and heat transfer reduction. Pasupathy et al. (Pasupathy et al. 2008) have tested PCM
incorporation over roof for Chennai through direct incorporation. However, long
term impact was not carried out. Kant et al. (2017) carried out CFD simulation for
PCM integrated brick, for March 15, in Rae Barelli, India. Temperature of different
sections of bricks at different time of day was simulated. PCM suitability however,
has not been studied in any of these studies.
The testing of PCM bricks in actual conditions under various PCM configurations has been carried out by Saxena et al. (2019). For this purpose, modified mud
bricks were prepared using conventional Indian brick making process, as it is well
established and could be scaled for future applications. The experiments were carried
out for peak summer conditions with ambient temperature of 40 °C and above. The
reduction of 6 °C was observed. Heat transfer reduction up to 12% was observed.
13.6 PCM Thermal Conductivity Enhancement
with Nanoparticle Dispersion
Owing to the low thermal conductivities of PCMs there has been a considerable effort
towards enhancement of thermal conductivity thereby increasing the dispatchability
of TES systems. Inorganic PCMs are cheap and have better thermal conductivities
than the organic PCMs however their stability over large number of cycles of charging
and discharging is still an issue. Tendency of super-cooling is also higher in the case
of inorganic salts. Due to super-cooling, the PCM is to be cooled below the freezing
point temperature before it actually starts freezing and release heat. More importantly, it would not solidify unless this lower (nucleating) temperature is reached.
However, the accompanying temperature in the new cycle it only absorbs the sensible
heat. Thus, the usability of the inorganic PCMs is significantly lowered. Apart from
this, inorganic materials also have compatibility issues with metal containers etc.
Table 13.3 compares inorganic and organic PCM.
The researchers across the globe are working to overcome the problem of low
thermal conductivities of PCMs. Particularly for organic PCMs, thermal conductivity
enhancement seems to be only issue that is to be addressed for which a number of
solutions have been suggested in the literature. The researchers are aiming at creating
composite materials by enhancing organic PCMs using metallic foam, nano-particles
of metal oxides and carbon. Babapoor and Karimi (2015) compared the results of
adding SiO 2 , Al 2 O 3 , Fe 2 O 3 , ZnO nano to PCMs to create a nano enhanced PCM
(NEPCM). Of these, Al 2 O 3 nano was found to give best results in terms of thermal
conductivity enhancement. A comparison was made using DSC for different metal
oxide nanoparticles including Al 2 O 3 and TiO 2 being added to medium temperature
PCM (Teng and Yu 2012). It was found that, of the five metal oxide nanoparticles,
TiO 2 was the best.
R. Saxena et al.
conditions in India. PCMs showed better results in terms of temperature reduction
and heat transfer reduction. Pasupathy et al. (Pasupathy et al. 2008) have tested PCM
incorporation over roof for Chennai through direct incorporation. However, long
term impact was not carried out. Kant et al. (2017) carried out CFD simulation for
PCM integrated brick, for March 15, in Rae Barelli, India. Temperature of different
sections of bricks at different time of day was simulated. PCM suitability however,
has not been studied in any of these studies.
The testing of PCM bricks in actual conditions under various PCM configurations has been carried out by Saxena et al. (2019). For this purpose, modified mud
bricks were prepared using conventional Indian brick making process, as it is well
established and could be scaled for future applications. The experiments were carried
out for peak summer conditions with ambient temperature of 40 °C and above. The
reduction of 6 °C was observed. Heat transfer reduction up to 12% was observed.
13.6 PCM Thermal Conductivity Enhancement
with Nanoparticle Dispersion
Owing to the low thermal conductivities of PCMs there has been a considerable effort
towards enhancement of thermal conductivity thereby increasing the dispatchability
of TES systems. Inorganic PCMs are cheap and have better thermal conductivities
than the organic PCMs however their stability over large number of cycles of charging
and discharging is still an issue. Tendency of super-cooling is also higher in the case
of inorganic salts. Due to super-cooling, the PCM is to be cooled below the freezing
point temperature before it actually starts freezing and release heat. More importantly, it would not solidify unless this lower (nucleating) temperature is reached.
However, the accompanying temperature in the new cycle it only absorbs the sensible
heat. Thus, the usability of the inorganic PCMs is significantly lowered. Apart from
this, inorganic materials also have compatibility issues with metal containers etc.
Table 13.3 compares inorganic and organic PCM.
The researchers across the globe are working to overcome the problem of low
thermal conductivities of PCMs. Particularly for organic PCMs, thermal conductivity
enhancement seems to be only issue that is to be addressed for which a number of
solutions have been suggested in the literature. The researchers are aiming at creating
composite materials by enhancing organic PCMs using metallic foam, nano-particles
of metal oxides and carbon. Babapoor and Karimi (2015) compared the results of
adding SiO 2 , Al 2 O 3 , Fe 2 O 3 , ZnO nano to PCMs to create a nano enhanced PCM
(NEPCM). Of these, Al 2 O 3 nano was found to give best results in terms of thermal
conductivity enhancement. A comparison was made using DSC for different metal
oxide nanoparticles including Al 2 O 3 and TiO 2 being added to medium temperature
PCM (Teng and Yu 2012). It was found that, of the five metal oxide nanoparticles,
TiO 2 was the best.