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Case Study

Thermal Comfort Conditions of a Small-scale Tropical Enclosed Giant Freshwater Prawn (Macrobrachium rosenbergii) Hatchery: A Case Study

Emy Yusliza Zolkefli, Sabarinah Sh Ahmad, Mohd Salleh Kamarudin, Che Roos Saad, Mohd Fakri Zaky Jaafar and Jamarei Othman

This study was conducted to determine the thermal comfort conditions of a typical small-scaled enclosed freshwater prawn hatchery building. The thermal environment and comfort conditions were determined using in situ measurement for 12 continuous days and simulations. A small-scaled commercial hatchery at Sg Besar, Selangor was chosen for this study. The multi-data loggers were placed in selected area of hatchery building and the parameters measured were temperature (indoor, outdoor and water), light (indoor and water) and Relative Humidity (RH) (indoor and outdoor). The results showed that the indoor air temperature remained above comfort limit temperature (28.6°C) between 0900 and 1900 h beyond the working period (0700-1900 h). The water temperature remained above the optimal culture temperature (30°C) and reached the lethal limit (33°C) during the day. The average indoor relative humidity fell below outdoor relative humidity over the most of daytime and above the outdoor relative humidity at nighttime. The results indicated that daytime thermal environment in the hatchery building was extremely uncomfortable to the workers most of the time and at certain time could also detrimental to larval prawn growth.

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Emy Yusliza Zolkefli, Sabarinah Sh Ahmad, Mohd Salleh Kamarudin, Che Roos Saad, Mohd Fakri Zaky Jaafar and Jamarei Othman, 2011. Thermal Comfort Conditions of a Small-scale Tropical Enclosed Giant Freshwater Prawn (Macrobrachium rosenbergii) Hatchery: A Case Study. Journal of Fisheries and Aquatic Science, 6: 867-879.

DOI: 10.3923/jfas.2011.867.879

Received: August 30, 2011; Accepted: November 26, 2011; Published: December 30, 2011


Giant freshwater prawn, Macrobrachium rosenbergii is grouped in caridean crustacean belonging to the family Palaemonidae (Rabanal and Soesanto, 1985). Indigenous of the Asia-Pacific region, M. rosenbergii is better known as the giant Malaysian prawn and has become a major globally cultured species. Over the last decade, its total annual production had doubled up to 207,749 tons in 2008 which worth USD 1.1 billion (FAO, 2010). China, Thailand and Bangladesh are three main producers of M. rosenbergii.

In the South-east Asian regions including Malaysia, the backyard hatcheries are still the back bone in supplying the M. rosenbergii fry (Angel, 1994). There is a growing trend among the Malaysian prawn hatchery operators to conduct the larviculture in enclosed buildings to keep the buildings warm in the evenings as the night rearing water temperature in an open shed could reach or nearing the lower lethal temperature, 24°C (Tayamen, 2001).

In aquaculture, enclosed buildings are used to shelter the production unit from the environmental factors such as wind, rain, cold, heat, excessive light and improve the working environment for the workers (Lekang, 2007). However, the main purposes for an enclosed aquaculture building are to maintain controlled environmental conditions and provide biosecurity by minimising the infestation of insects dust and spread of pathogens into the culture system (Correia et al., 2000). Singh and Marsh (1996) stated that the utilization of temperature-controlled building or hatchery building is to maintain the inside warm temperature while warding off cold temperature from entering the building. The enclosed building designs for the temperate and cold climatic regions may not be suitable for the tropical regions as the latter main design challenge is to maintain an optimal rearing temperature for the cultured species and workers’ thermal comfort by warding off excessive heat during the day and possible cooling temperature after the midnight.

ISO 7730 Standard defines thermal comfort for human as a condition of mind which expresses satisfaction with the thermal environment (ISO 7730, 1994). While most researchers agree with the definition, the term cannot be not easily converted into physical parameters (Olesen, 2000). An enclosed environment will cause the human body to exchange heat by conduction, convection and radiation (Gadi, 2000a). The temperature difference between the body and the enclosing surfaces were affected the rate of radiative heat exchange (Gadi, 2000b). According to De Waal (1993), air movements in a enclosed building need to be set between 0.1 to 1.5 m sec-1 to provide an indoor thermal comfort. It because effect from increasing air movements from 0.1 to 0.5 m sec-1 gives an increase in maximum comfort temperature of some 3°C and further increase to 1.0 m sec-1 results in additional 1°C. However, air movement cannot increase rapidly and if greater than 1.5 m sec-1 become annoying during the day. Maximum air movement during night is 1.0 m sec-1.

Comfort is a major concern of the Heating Ventilating and Air Conditioning (HVAC) industry. Three main factors that can affect the human comfort are effective temperature, moisture content of air (relative humidity) and air motion (Hussein et al., 2001). American Society of Heating, Refrigerating and Air-conditioning Engineers, ASHRAE (1993) quantifies parameters of a room or space for the comfort zone in the summer season as dry bulb temperature of 22-27°C, relative humidity of 30-60% and air motion velocity of about 15 m min-1.

In addition to the above parameters, other factors affecting the human comfort are heat production and regulation in human body, cold and hot surfaces and air stratification. The deep human body temperature is about 37°C, whilst the human skin temperature can vary between 31°C and 34°C under comfort conditions (Auliciems and Szokolay, 1997). Human occupants are less sensitive to relative humidity rather than variation of temperature (Hussein et al. 2001). The knowledge of thermal comfort behaviour of human and energy utilization behavior of buildings are important to give the best strategy to develop in a sustainable manner.

The thermal conditions of the enclosed aquaculture buildings in the tropical conditions especially Malaysia have not been studied. A thermal discomfort condition in an enclosed building can be easily developed in Malaysia because it is hot and humid tropical country and has a yearly mean temperature of between 26 to 27°C (Sabarinah, 2006). This research was conducted to study the thermal conditions and the suitability of the building design of a small-scaled hatchery building for the Malaysian giant freshwater prawn, M. rosenbergii. The information gathered would be useful for the designing of an ideal enclosed hatchery building that can provide better indoor conditions for the workers and an optimal larval prawn growth (Sandifer and Smith, 1985).


Case study: This study was carried out at Annur Hatchery, Bagan Terap, Sungai Besar, Selangor Darul Ehsan, Malaysia (Fig. 1). This hatchery is located at latitude 3°44’53.0” N and longitude 101°3’12.0” E. The orientation of hatchery building is 292.5°C.

The building was 12.1 m wide, 18.2 m long and 3.0 m high. This hatchery building has a production unit for larval rearing, a small office and a store. The plan layout of hatchery building are small scale hatchery (Fig. 2-6). This hatchery represented a typical small scale backyard prawn hatchery in Malaysia and was constructed mainly from recycled building materials such as used metal and non-asbestos fiber sheets for the roof and walls and used planks for the walls of the office and store. The wall and roofs were not insulated against heat transmission. A portion of the roof was made transparent using acrylic sheets. The hatchery building are constructed with complete materials with different thickness (Table 1).

Fig. 1: A small-scale giant freshwater prawn hatchery at Sungai Besar, Selangor, Malaysia

Table 1: Construction materials and thickness
aConstruction materials provided in the simulation software

Fig. 2: Hatchery building model (Axonometric, 3D view)

Fig. 3: Front elevation of the building

Fig. 4: Side elevation of the building

Field measurement: The data measurements were collected for 12 days from 25 November to 6 December 2007. During the measurement, all doors and windows in the production unit remained closed. Typography measurement and in situ indoor, outdoor and water parameters (temperature, relative humidity, light intensity) were recorded using Hobo multi-data loggers (Onset, USA). The multi-data loggers were placed at selected locations in the hatchery (Hobo U12) and culture tanks (HOBO® Temperature/Light Waterproof Pendant). In the production unit there were 10 rectangular fiberglass tanks with size 2.5 m wide, 7 m long and 4 m high.

Simulation: Beside the in situ measurements, the thermal conditions in the building were also simulated using Integrated Environmental Solutions (IES) Virtual Environment version 5.6 (Integrated Environmental Solutions (IES) Limited, 1994). The construction properties are:

Alesorptance for solar radiation: 0.55
Emissivity: Both for inside and outside of opaque surface: 0.90
Air infiltration: 1 ach
Cooling mechanism: Natural ventilation
Incoming of air: Natural (external air)
Building orientation: 292.5°

Fig. 5: Top elevation of the building

Fig. 6: Floor plan of the hatchery building. a: Office, b: Hallway, c: Store room, d: Culture (no wall), e: culture room

The building operated 7 days per week at 12 h per day (0700 to 1900 h). The internal gain of the building was from two workers:

Max. sensible gain : 90 W per person (90 Wx2 person = 180 W)
Max. latent gain : 60 W per person (60 Wx2 person = 120 W)

The simulations were performed using the nearest climatic data, Kuala Lumpur, Malaysia provided by ASHRAE.


In situ measurement: The profiles of measured indoor and outdoor temperature in the hatchery building and water temperature in the larviculture tanks (Fig. 7-8). The indoor and outdoor and water temperature fluctuated during the study within 23.55-41.24°C, 23.63-35.49°C and 25.71-32.74°C, respectively.

Fig. 7: Measured temperature (outdoor, indoor and water)

Fig. 8: Average daily measured temperature

The highest indoor temperature recorded was 41.24°C on 2nd Dec at 16:00 h while the highest water temperature of 32.74°C was seen on 1st Dec. at 1345 h. The average daily indoor, outdoor and water temperature ranged 25.06-37.52°C, 25.43-33.48°C and 26.78-30.98°C, respectively.

The hatchery operated from 07:00 to 19:00 h daily. Generally, the indoor air temperature was significantly higher than outdoor temperature almost 0.39% of the working hour. The indoor and outdoor relative humidity (RH) ranged 43.51-82.25 and 50.01-79.21%, respectively (Fig. 9, 10). The average RH was lower than outdoor RH in hatchery building during most of the daytime and became higher than the outdoor RH at nighttime. Indoor RH ranged 43.51-82.15% during the daytime.

The average indoor Light Intensity (LI) was measured during the study (Fig. 10). The daytime indoor LI ranged between 34 to 5567.42 lux observed at 1415 h. The daytime water LI ranged 293.26-4066.14 lux and was always lower than indoor LI.

The indoor air temperature with tank water temperature of hatchery building showed the correlation (Fig. 11). The rising and cooling indoor air temperature occured between 0645 to 1415 h and 1415 to 0645 h, respectively. A similar pattern was observed in the water temperature with a 0.5h delay from the indoor air temperature. When these delayed rising and cooling temperatures were plotted against the indoor air temperature (Fig. 12, 13), the following linear equations were obtained.

Fig. 9: Average daily measured relative humidity

Fig. 10: Average daily measured light intensity

Fig. 11: Average daily indoor air temperature and eater temperature in tanks

Fig. 12: Average daily indoor air temperature and water temperature in tanks

Fig. 13: Correlation for rising temperature pattern of indoor air temperature vs. water temperature

Fig. 14: Measured and simulated indoor air temperature (25 Nov. to 6 Dec. 2007)

Fig. 15: Simulated indoor air temperature on hottest (March) and coolest months (Dec.)

Fig. 16: Simulated indoor air temperature on hottest (March) and coolest months (Dec.)

Rising Tw = 0.2717 Ti+20.749 (R2 = 0.7830)
Cooling Tw = 0.2531 Ti+21.308 (R2 = 0.7665)
where Tw = tank water temperature and Ti = indoor air temperature

Simulation: The thermal conditions of hatchery building were simulated for hottest (March) and coolest (December) months. The profiles of measured and simulated indoor air temperature are shown for verification and comparison (Fig. 14). The simulated indoor air temperature were similar with measured temperature for most of the days except on 29th November.

The simulated indoor air temperature and tank water temperature were obtained on hottest and coolest month (Fig. 15, 16). The highest indoor and water temperature in the hottest month were 48.54°C and 33.80°C, respectively while the temperature in the coolest month were 40.77°C and 31.81°C, respectively. The indoor and water temperature on the peak days in the hottest month on 2nd March and coolest month on 6th December (Fig. 17). The average simulated indoor and water temperature were obtained in hottest and coolest months (Fig. 18).

Fig. 17: Peak day simulation on hottest (March) and coolest (Dec.) month

Fig. 18: Average day simulation on hottest (March) and cooles (Dec.) month

The indoor air temperature on hottest and coolest months ranged 24.07-41.46°C and 23.79-38.11°C, respectively. The average water temperature in hottest and coolest months ranged 27.29-32.01°C and 27.21-31.10°C, respectively.


ASHRAE (1993) recommended that thermal comfort indoor conditions in a tropical building should fall within 30 to 60% for RH and 22 to 27°C for temperature. However, in general, the daytime indoor air temperature and relative humidity in the naturally ventilated studied building were much higher than ASHRAE recommended levels. The daytime indoor air temperature also remained above the upper comfort limit (28.6°C) for human (Sabarinah, 2006) and even reached higher than 40°C for 6.25% of the working hours.

Zainal and Keong (1996) reported that Malaysian factory workers can tolerate up to 26°C indoor air temperature while.Sabarinah (2006) found that the neutrality temperature for naturally ventilated buildings in Malaysia is 26.1°C while Abdul Rahman and Kannan (1997) reported a higher neutrality temperature (27.4°C). Unfavorable thermal conditions in a hatchery cause thermal discomfort amongst the workers which leads to lower productivity (Lan et al., 2009). An indoor temperature above 40°C creates an unhealthy environment to the workers (Auliciems and Szokolay, 1997) while prolonged exposure to high indoor temperature will cause extreme thermal discomfort and may lead to heat stroke when the body temperature reaches about 40°C (Auliciems and Szokolay, 1997).

The optimal water temperature for M. rosenbergii larviculture is 28-30°C (Tayamen, 2001). At night, the water temperature in the studied hatchery could drop to 25.71°C and remained under 28°C between 0115-0915 h. During the day, the water temperature remained above 30°C between 1115-1730 h and even reached 32.74°C which was nearing the upper lethal temperature limit for the prawn larvae (Tayamen, 2001). The occasional unexplained high mortality or total larval loss reported by the hatchery operator could be related to the upper lethal temperature limit of the larval prawns being compromised.

An indoor light intensity of 2500 to 6500 lux is needed in a green water prawn larviculture system to promote beneficial algal growth in the tanks (Tayamen, 2001). The algae play an important role to keep toxic ammonia in the water at a low and safe level. Sufficient sunlight penetrated the hatchery production area through transparent portions of the roof which a common and typical feature of prawn hatcheries (Hsieh et al., 1989). The transparent roof portions were made of acrylic without heat or UV blocking feature. The roof combination of non heat blocking transparent acrylic and uninsulated metal sheets worsened the indoor thermal conditions of the hatchery as excessive solar radiation and light produce excessive heat especially during warmer months (Valenti and Daniels, 2000). In the Indian hatcheries, silpaulin are commonly used as the roof material (Raju and Nair, 1992).

This study showed that the design of the building failed to provide comfortable indoor conditions for workers and optimal larviculture conditions for the prawn. Specifying the right materials for building construction is one of the important aspects in designing thermal comfort buildings. The internal thermal condition of the building can be directly determined through the thermal conductivity of the materials. Mutaf et al. (2004) focused their research on the effects of summer and winter natural ventilation air exchange on psychromatic of closed and open type poultry houses. To increase the efficiency of natural ventilation, they proposed the roof of the enclosed building to be fitted with slope of not less than 20-30° and the ridge fitted with continuous capped ventilation which remains open. The ridge should not be less than 4-5 m high while the building width should not exceed 12 m. However, these recommendations may not be suitable for a prawn hatchery as some light penetration is needed for the larviculture while prawns are poikilothermic animals which do not generate heat.

Jayasinghe et al. (2003) reported that the use of appropriate roofing materials and insulation can reduce the excessive heat transferred through the roof and enhance the indoor thermal comfort. However, they found that the building orientation provide no significant effect on the thermal performance of the building. A further study exploring the use of roofing materials and insulation through simulation should be conducted to improve the indoor thermal conditions of the hatchery for the workers and prawn larviculture.


This study showed that simulation can be used as a tool to assess the indoor thermal conditions of a prawn hatchery as its results were comparable to measured data. The results showed the hatchery failed to provide the optimal thermal rearing conditions for the prawn larvae. In addition, the building could not sufficiently provide thermal comfort conditions for the workers during the working hours.


The authors wish to thank Ministry of Science, Technology and Innovation (MOSTI) for funding this project under the project number 03-01-01-SF007 and to En Nordin Salimin, the owner’s of the Annur Hatchery for the cooperation.

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