Performance Analysis on the Optimum Control of a Calorimeter with a Heat Recovery Unit for a Heat Pump

Heat pumps are used in many applications, both in households and industries, for space air conditioning and hot water provision. The calorimeter is the equipment used in testing the heat pump system to obtain performance data. In the conventional testing mode and under standard conditions, the calorimeter utilizes a lot of energy through refrigeration and heating systems. In this study, a newly developed calorimeter with a heat recovery unit was used to test the performance of a water-to-water heat pump system. The aim was to minimize the rate of energy used in the conventional calorimeter. Two heat recovery control methods were adopted. In the control (1), the heat recovery unit was used to control the inlet water temperature setpoint for the heat pump indoor heat exchanger, whereas in control (2), the heat recovery unit was used to control the inlet water temperature setpoint for the heat pump outdoor heat exchanger. Tests were executed by varying the operating mode and test conditions. For the heating operating mode, the inlet water setpoint temperatures for the indoor and outdoor heat pump heat exchangers were 40 °C and 5 °C, respectively, whereas for the cooling mode, the inlet water setpoint temperatures for the outdoor and indoor heat pump heat exchangers were 25 °C and 12 °C, respectively. The analyses of the experimental results revealed that the energy saving of the calorimeter with heat recovery was about 71% in cooling mode and 73% in heating mode compared to the conventional calorimeter. Also, the energy consumption of the proposed calorimeter was analyzed based on the control methods. In heating mode, the calorimeter performance was enhanced when the control (2) strategy was used because the energy saving was about 8 to 13% compared to control (1). However, in the cooling mode test, it was the control (1) method that resulted in energy savings of about 6.4 to 21% compared to the control (2) method

Modeling and Simulation Performance Evaluation of a Proposed Calorimeter for Testing a Heat Pump System

The energy consumption for heating and cooling in the building sector accounts for more than one-third of total energy used worldwide. In view of that, it is important to develop energy efficient cooling and heating systems in order to conserve energy in buildings as well as reduce greenhouse gas emissions. In both commercial and residential buildings, the heat pump has been adopted as an energy efficient technology for space heating and cooling purposes as compared to conventional air conditioning systems. However, heat pumps undergo standard testing, rating, and certification procedures to ascertain their system performance. Essentially, the calorimeter for testing heat pumps has two test chambers to serve as a heat source and heat sink to control and maintain the test conditions required to simulate the heat pump indoor and outdoor units, simultaneously. In air-to-air heat pump units, the conventional calorimeter controls the air temperature and humidity conditions in each test chamber with separate air handling units consisting of a refrigerator, heater, humidifier, and supply fan, which results in high energy consumption. In this study, using dynamic modeling and simulation, a new calorimeter for controlling air conditions in each test chamber is proposed. The performance analysis based on simulation results showed that the newly proposed calorimeter predicted at least 43% energy savings with the use of a heat recovery unit and small refrigerator capacity as compared to the conventional calorimeter that utilized a large refrigerator capacity for all the weather conditions and load capacities that we investigated

Analysis of indoor set-point temperature of split-type ACs on thermal comfort and energy savings for office buildings in hot-humid climates

In hot-humid climates, particularly in sub-Saharan Africa (SSA), ambient temperatures and relative humidity are as high as 35 °C and 84%, respectively, requiring the use of mechanical cooling systems for indoor thermal comfort. Split-type vapor-compression air-conditioners (SVAC) are mainly used for space cooling in SSA and consume 60–80% of total energy consumption in commercial and public buildings. Appropriate control strategy of the indoor set-point temperature of SVAC can result in significant energy savings in these buildings. In this study, modeling and dynamic simulation have been conducted using EnergyPlus to predict the energy saving potential and indoor thermal comfort of buildings in hot-humid climates by controlling set-point temperature of the SVAC. In a case study, climatic data for Ghana, was used to predict the energy saving potential and indoor thermal comfort. The study results revealed that, to ensure indoor thermal comfort at high outdoor temperature condition of 35 °C, the least and optimum set-point temperatures of the SVAC should be 21 °C and 25 °C, respectively. On the other hand, for low outdoor temperature condition, the least and optimum set-point temperatures were 22 °C and 26 °C, respectively. Considering 1-star and 2-star rated SVACs which are dominantly used in Ghana, operating at 21–25 °C in the case of high outdoor conditions, and 22–26 °C for low outdoor conditions relative to the least temperatures resulted in energy savings of 8–33% and 12-44%, respectively

Performance Analysis of a Mechanical System To Break and Separate Palm Nut-Fibre Cake

This research seeks to test the performance of a palm nut-fibre cake breaker and separator machine to alleviate the problem of hand separation by local oil producers. It takes into consideration the standard cylindrical shape of a palm nut-fibre cake. The machine operated on an electric motor of 2.2 kW at 1420 rpm. The average throughput capacity of the machine was 107.72 kg/hr with the capacity weight of 120 kg. Test results indicated a separation efficiency of 92%. Also, cost estimation indicated that the annual savings in using the machine with less labour than manual labour entirely was $466. The study outcome is relevant to small-scale producers on the need to utilize a cost-effective machine to facilitate a high separation yield of nuts and fibres from the cake obtained from processing palm oil and improve the production output of palm kernel oil processed from the nuts

Efficient control of cascade heat pumps using variable speed compressors

Building load varies continuously throughout the year, causing heat pumps to operate at part load. At such situations, the capacity of the heat pump needs to be controlled to meet the building load. The use of variable speed compressors to control the capacity of heat pumps is found to be the most energy-efficient. However, the efficient control of the capacity of the cascade heat pump using variable speed compressors is lacking in the open literature. This study investigates an energy-efficient capacity control method for a cascade heat pump by adopting variable speed compressors to match the rated capacity of a cascade heat pump at varying indoor and outdoor entering water temperature (EWT) conditions. Three capacity control strategies were employed in this study namely: low temperature (LT) compressor speed control, high temperature (HT) compressor speed control, and simultaneous LT and HT compressor speed control. COP of the cascade heat pump was almost similar in simultaneous control of the LT and HT compressor speeds and HT compressor speed control but significantly higher in simultaneous LT and HT compressor speed control than LT compressor speed control at all outdoor EWT conditions. However, the cascade heat pump had no significant difference in its COP at varying indoor EWT using all three capacity control strategies. It is recommended that water-to-water cascade heat pumps adopt variable speed compressors at the HT side and constant speed compressors at the LT side for efficient and cost effective capacity control at varying building loads

Investigating The Failure of Leaf Springs in Automobile Suspension on Ghana Road

This study investigates the failure of leaf springs used in the suspension system of heavy-duty vehicles in Ghana. Primary and secondary data were collected using both open and closed-ended questionnaires. Welders and fabricators of Sarkyoyo enterprise at the Suame Spare parts dealership area in Kumasi were engaged in the survey. The elastic strain and stress mathematical models were used to determine the stress points in a loaded leaf spring with the aid of ANSYS. The factors considered in the analysis were the leaf spring SAE design specification, the recommended Ghana Highway Authority load limit for heavy-duty vehicles, and the terrain. Analysis was done for both the standard and variable curvature leaf springs. The mode of failure was found to be fatigue loading. The causes of failure were determined to be loaded beyond the recommended 43 tons per wheel limit, bad roads, and reckless driving. It was also observed that loading causes the edges of the leaf spring to bend outwardly from the top, making the edges more prone to failure. Results further showed that the leaf spring with variable curvature recorded strain energy 2.5 times higher than the standards leaf spring

Assessment of Automobile Engines Rebuilt at Local Artisan Workshops in Ghana

The manufacturing industry of Ghana, as promising as it is, has many shaping to be done. This specifically goes to the automobile manufacturers and engine rebuilders of Ghana. Though agile and very skillful in rebuilding engines many have reported grievances on their service renders to them. This shows that, the knowledge and zeal to rebuild it puts the industry at a certain level but needs further additional and requisite tuning to reach the pinnacle. For this reason, the researcher therefore sought to investigate how cylinder bores and piston ring end-gap contribute to the failure of locally rebuilt engines. A descriptive design was used for the study and sample of 60 participants responded to the structured questionnaire. The study used primary data to provide reliable and up-to-date information the researcher needs for the analysis. The data were entered in SPSS with analysis performed using inferential and descriptive analysis methods. The findings of the study revealed that errors made in the work procedure had a stronger effect on the clients’ than its other counterpart. Practically, the flaws in the work procedure of rebuilding cylinder bore significantly affects clients’ satisfaction